Systems and methods for entropy quantum computing

Abstract

Provided herein are systems for quantum information processing implementing an entropy quantum computing (EQC) framework and methods of operating quantum information processing systems implementing an EQC framework. A quantum information processing system may include a quantum register comprising an array of qudit components, a qudit coherent control system coupled to the quantum register and configured to exert a coherent state transformation to the qudit components of the quantum register, and a controlled entropy source configured to couple to the qudit components of the quantum register to apply continuous or periodic measurement to the qudit components that are coupled to the controlled entropy source.

Description

SYSTEMS AND METHODS FOR ENTROPY QUANTUM COMPUTINGCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 481,904 filed January 27, 2023, the entire contents of which are incorporated herein by reference.TECHNICAL FIELD OF THE DISCLOSURE

[0002] The present disclosure relates to quantum data processing technology, including quantum computing, simulation, and optimization, particularly those suitable for implementation at room temperature and based on integrated optical or electronics circuits.BACKGROUND OF THE DISCLOSURE

[0003] Quantum data processing promises significant advantages in information computing speed, capacity, and security. It uses quantum mechanical effects to simulate many-partite dynamics, find the solution of large-scale problems, and provide predictive analyses for complex systems. A well-known quantum data processing paradigm is quantum computing, where quantum tunneling, quantum adiabatic passage, and / or quantum logic operations are employed to solve optimization problems that prove to be challenging for digital computers based on classical physics. Such systems conventionally include preparing a quantum state with high purity, evolving the quantum state under certain Hamiltonians that could be time dependent and / or comprise many logic operations, and ultimately measuring the resulting quantum state to read out the information for solutions. A significant challenge with such systems is the requirement to prepare and evolve quantum states with high purity, which in practice requires a well-behaved, quantum closed system — i.e., a well-isolated system that has little coupling with its surrounding environment and is shielded from thermal, electromagnetic, mechanical and gravitational background.

[0004] Indeed, quantum states are typically very sensitive to noise and decoherence, which may quickly result in loss of quantum signatures and information. As such, typical quantum computing devices employ quantum objects housed in near absolute-zero temperature and high vacuum conditions. As such, conventional quantum computers are subject to several inherent limitations. First, the need for such demanding housing adds significant operation overhead. Second, these closed systems are still fragile to external disturbances. Third, many such systems have limited connectivity, meaning that theinteraction between the quantum objects is limited to among the nearest neighbors, or practically achievable only with a small fraction of the quantum objects. Fourth, for those based on the adiabatic passage, the evolution time of the system must be long enough to satisfy the adiabatic condition, resulting in a limited information processing speed.BRIEF SUMMARY OF THE DISCLOSURE

[0005] In some embodiments, provided herein is a quantum information processing system comprising a quantum register comprising an array of qudit components, wherein each qudit component comprises at least two quantized states; a qudit coherent control system coupled to the quantum register and configured to exert a coherent state transformation to the qudit components of the quantum register; and a controlled entropy source configured to couple to the qudit components of the quantum register to apply continuous or periodic measurement to the qudit components that are coupled to the controlled entropy source.

[0006] In any of these embodiments, the qudit coherent control system may comprise at least one pumping laser that coherently changes or amplifies the states of the qudit components of the quantum register. The term “changes or amplifies the states of the qudit components” refers to effectuating a change in the quantum state of the qudit components, for example effectuating a change in the contributions of individual states to a superposition or amplifying a given state in a superposition by increasing the contribution to the superposition from said amplified state. In any of these embodiments, the controlled entropy source may comprise an array of focused laser beams or electro-optical modulation devices. In any of these embodiments, each of the qudit components of the quantum register may be a single atom, a single ion, or a single photon. In any of these embodiments, the coherent state transformation may be a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the controlled entropy source may apply continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state. In any of these embodiments, the quantum information processing system may further comprise a quantum measurement port coupled to the qudit components of the quantum register and configured to receive measurement results from the qudit components of the quantum register; and a feedback control unit, wherein the feedback control unit couples the quantum measurement port and the controlled entropy source and is configured to generate controlling sequences from the measurement results received by the quantum measurement port to control theentropy source and / or to modulate the coupling of the qudit components to the entropy source. In any of these embodiments, each of the qudit components may be a qubit that has two quantized states.

[0007] In some embodiments, also provided herein is a quantum information processing system comprising a quantum register comprising an array of qudit components, wherein each qudit component comprises at least two quantized states; a qudit coherent control system coupled to the quantum register and configured to exert a coherent state transformation to the qudit components of the quantum register; and a quantum feedback channel coupled to the quantum register, the quantum feedback channel configured to induce controlled loss of information to the qudit components of the quantum register according to the quantum states of the qudit components of the quantum register.

[0008] In any of these embodiments, the qudit coherent control system may comprise at least one pumping laser that coherently changes or amplifies states of the qudit components of the quantum register. In any of these embodiments, each of the qudit components of the quantum register may be a single atom, a single ion, or a single photon. In any of these embodiments, the quantum feedback channel may comprise an array of focused laser beams or electro-optical modulation devices. In any of these embodiments, each of the qudit components may be a qubit that has two quantized states.

[0009] In some embodiments, also provided herein is a method for operating a quantum information processing system, comprising applying a coherent control force to qudit components of a quantum register of the quantum information processing system to dynamically evolve the qudit components; and coupling at least one of the qudit components of the quantum register to a controlled entropy source of the quantum information processing system to apply measurement pulses to the subset of qudit components coupled to the controlled entropy source to alter the coherent dynamics of the qudit components through backactions induced by quantum measurements.

[0010] In any of these embodiments, the qudit components may all each initially be in a ground state. In any of these embodiments, at least one select qudit component may not be coupled to the controlled entropy source, and the method may further comprise maintaining the coherent control force and the coupling between the at least one qudit component and the controlled entropy source until the at least one select qudit component is in a desirable state. In any of these embodiments, the coherent control force may be a rotation force uniformlyapplied to the qudit components to simultaneously transition each of the qudit components to an excited state and the controlled entropy source may apply continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state.

[0011] In any of these embodiments, at least two select qudit components may not be coupled to the controlled entropy source, and the method may further comprise maintaining the coherent control force and the coupling between the at least one qudit component and the controlled entropy source while entangling the at least two select qudit components by subjecting the at least two select qudit components to joint measurement. Joint measurement refers to the coupling of joint quantum states of qudits to an external degree of freedom or to a plurality of external degrees of freedom in a way such that the coupling is dependent on the joint states of the qudits rather than the individual states. In any of these embodiments, the coherent control force may be a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the controlled entropy source may apply continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state.

[0012] In any of these embodiments, a first select qudit component may be initially in an arbitrary superposition state and the remainder of the qudit components may be initially in the ground state. In any of these embodiments, the subset of qudit components may not include the first select qudit component and at least one additional select qudit component of the quantum register, and the method may further comprise maintaining the coherent control force and the coupling between the at least one qudit component and the controlled entropy source while entangling the first and at least one additional select qudit components by subjecting the first and at least one additional select qudit components to joint measurement. In any of these embodiments, the coherent control force may be a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the controlled entropy source may apply continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state. In any of these embodiments, each of the qudit components may be a qubit that has two quantized states.

[0013] In some embodiments, also provided herein is a method for operating a quantum information processing system, comprising applying a coherent control force to qudit components of a quantum register of the quantum information processing system todynamically evolve the qudit components; and coupling at least one of the qudit components of the quantum register to a quantum feedback channel of the quantum information processing system to induce controlled loss of information to the qudit components of the quantum register according to the quantum states of the qudit components of the quantum register.

[0014] In any of these embodiments, the qudit components may all each initially be in a ground state. In any of these embodiments, at least one select qudit component may not be coupled to the quantum feedback channel, and the method may further comprise maintaining the coherent control force and the coupling between the at least one qudit component and the quantum feedback channel until the at least one select qudit component is in a desirable state. In any of these embodiments, the coherent control force may be a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the quantum feedback channel may apply continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state.

[0015] In any of these embodiments, at least two select qudit components may not be coupled to the quantum feedback channel, and the method may further comprise maintaining the coherent control force and the coupling between the at least one qudit component and the quantum feedback channel while entangling the at least two select qudit components by subjecting the at least two select qudit components to joint measurement. In any of these embodiments, the coherent control force may be a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the quantum feedback channel may apply continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state.

[0016] In any of these embodiments, a first select qudit component may initially be in an arbitrary superposition state and the remainder of the qudit components may initially be in the ground state. In any of these embodiments, the subset of qudit components may not include the first select qudit component and at least one additional select qudit component of the quantum register, and the method may further comprise maintaining the coherent control force and the coupling between the at least one qudit component and the quantum feedback channel while entangling the first and at least one additional select qudit components by subjecting the first and at least one additional select qudit components to joint measurement.In any of these embodiments, the coherent control force may be a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the quantum feedback channel may apply continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state. In any of these embodiments, each of the qudit components may be a qubit that has two quantized states.

[0017] A significant advantage of the systems and methods described herein is that the quantum system can be evolved into a stable quantum state, which is largely immune to decoherence and noise. Such stability will allow operation over long time and with many particles, as needed to solve realistic problems. The systems and methods described herein help to ameliorate the need for cryogenic and vacuum housing and afford stable, durable, and robust operation at room temperature and in ambient environment.BRIEF DESCRIPTION OF THE FIGURES

[0018] For a more complete understanding of the present disclosure, reference is made to the following detailed description of exemplary embodiments considered in conjunction with the accompanying drawings.

[0019] FIG. 1 is a schematic diagram of a quantum open system to explain the principle of operation in accordance with an embodiment of the present disclosure.

[0020] FIG. 2 is a schematic diagram of a time-dependent environment for EQC realized in a cavity-QED system in accordance with an embodiment of the present disclosure.

[0021] FIG. 3 is a schematic diagram of a spectrum-dependent environment for EQC realized in a cavity-QED system in accordance with an embodiment of the present disclosure.

[0022] FIG. 4 is a schematic diagram of controlled coupling between a quantum object with electromagnetic vacuum in accordance with an embodiment of the present disclosure.

[0023] FIG. 5 is a schematic diagram of a multiport circuit for quantum state transformation modified by using EQC principles in accordance with an embodiment of the present disclosure.

[0024] FIG. 6 is a schematic diagram of quantum logical operations between two objects through engineered environment in accordance with an embodiment of the present disclosure.

[0025] FIG. 7A is a block diagram of a quantum information processing system in accordance with one or more embodiments.

[0026] FIG. 7B is a block diagram of a quantum information processing system in accordance with one or more embodiments.

[0027] FIG. 7C is a block diagram of a quantum information processing system in accordance with one or more embodiments.

[0028] FIG. 7D is a block diagram of a quantum information processing system in accordance with one or more embodiments.

[0029] FIG. 7E is a block diagram of a quantum information processing system in accordance with one or more embodiments.

[0030] FIG. 7F is a block diagram of a quantum information processing system in accordance with one or more embodiments.

[0031] FIG. 7G is a block diagram of a quantum information processing system in accordance with one or more embodiments.

[0032] FIG. 7H is a block diagram of a quantum information processing system in accordance with one or more embodiments.

[0033] FIG. 8A is a block diagram of a quantum information processing system in accordance with one or more embodiments.

[0034] FIG. 8B is a block diagram of a quantum information processing system in accordance with one or more embodiments.

[0035] FIG. 8C is a block diagram of a quantum information processing system in accordance with one or more embodiments.

[0036] FIG. 8D is a block diagram of a quantum information processing system in accordance with one or more embodiments.

[0037] FIG. 9 is a flowchart of a method for operation a quantum information processing system in accordance with one or more embodiments.

[0038] FIG. 10 is a flowchart of a method for operation a quantum information processing system in accordance with one or more embodiments.

[0039] FIG. 11 is a flowchart of a method for operation a quantum information processing system in accordance with one or more embodiments.

[0040] FIG. 12 is a flowchart of a method for operation a quantum information processing system in accordance with one or more embodiments.

[0041] FIG. 13 is a flowchart of a method for operation a quantum information processing system in accordance with one or more embodiments.

[0042] FIG. 14 is a flowchart of a method for operation a quantum information processing system in accordance with one or more embodiments.

[0043] FIG. 15 is a flowchart of a method for operation a quantum information processing system in accordance with one or more embodiments.

[0044] FIG. 16 is a flowchart of a method for operation a quantum information processing system in accordance with one or more embodiments.

[0045] FIG. 17 is a flowchart of a method for operation a quantum information processing system in accordance with one or more embodiments.

[0046] FIG. 18 is a flowchart of a method for operation a quantum information processing system in accordance with one or more embodiments.

[0047] FIG. 19 is a flowchart of a method for operation a quantum information processing system in accordance with one or more embodiments.

[0048] FIG. 20 is a flowchart of a method for operation a quantum information processing system in accordance with one or more embodiments.

[0049] FIG. 21 is an illustration of single qubit logic operations performed with a quantum information processing system in accordance with one or more embodiments.

[0050] FIG. 22 is an illustration of conditional logical operations between qubits performed with a quantum information processing system in accordance with one or more embodiments.

[0051] FIG. 23 is an illustration of conditional logical operations between qubits performed with a quantum information processing system in accordance with one or more embodiments.DETAILED DESCRIPTION OF THE DISCLOSURE

[0052] Detailed principles and embodiments of the present invention are disclosed. However, it is to be understood that the disclosed principles and embodiments are merely illustrative of the invention that may be embodied in various forms. In addition, each examplegiven in connection with or in accordance with the various embodiments of the current invention is intended to be illustrative, and not restrictive.

[0053] Provided herein are quantum information processing systems. In some embodiments, the quantum information processing system comprises a quantum register comprising an array of qudit components, wherein each qudit component comprises at least two quantized states; a qudit coherent control system coupled to the quantum register and configured to exert a coherent state transformation to the qudit components of the quantum register; and a controlled entropy source configured to couple to the qudit components of the quantum register to apply continuous or periodic measurement to the qudit components that are coupled to the controlled entropy source. A qudit component is a d-dimensional quantum information component. The term “coupled,” as used in the context of a qudit component means that the qudit components are bound to another component in a way that a change to the component coupled to the qudit component effectuates a change in the qudit component. A qudit coherent control system refers to a component of a quantum information processing system designed to control the states of qudit components. The coherent state transformation refers to the transformation of states of a quantum system without effectuating decoherence of the system. A controlled entropy source refers to an environment that has been attenuated in an advantageous manner in the context of quantum information processing. A controlled entropy source may, for example, refer to the environment of a quantum system where the noise from the environment influencing the quantum system has been attenuated to be non- Markovian.

[0054] In some embodiments, the qudit coherent control system comprises at least one pumping laser that coherently changes or amplifies the states of the qudit components of the quantum register. In some embodiments, a pumping laser is a device intended to induce optical pumping of a quantum system and may, for example, be used to transition (“pump”) qubits from the ground state to the excited state. In some embodiments, the controlled entropy source comprises an array of focused laser beams or electro-optical modulation devices. In some embodiments, an electro-optical modulation device is a device that can modulate light through an electro-optic effect and may modulate the light, for example, with respect to frequency, amplitude, or polarization. In some embodiments, each of the qudit components of the quantum register is a single atom, a single ion, or a single photon. In some embodiments, the coherent state transformation is a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excitedstate and the controlled entropy source applies continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state. A rotation force refers to a coherent state transformation that is a unitary transformation of the states of a quantum system and, given an arbitrary angle 0, effectuates a rotation of the population of quantum states of a quantum system by an angle 0. A rotation force may be used to transition a qubit from the ground state |0) to the excited state 11).

[0055] In some embodiments, the quantum information processing system further comprises a quantum measurement port coupled to the qudit components of the quantum register and configured to receive measurement results from the qudit components of the quantum register; and a feedback control unit, wherein the feedback control unit couples the quantum measurement port and the controlled entropy source and is configured to generate controlling sequences from the measurement results received by the quantum measurement port to control the entropy source and / or to modulate the coupling of the qudit components to the entropy source. A quantum measurement port is a component of a quantum information processing system capable of receiving and transmitting measurement results from qudit components of the quantum information processing system. A feedback control unit is a component of a quantum information processing system that modulates or amplifies measurement results to generate controlling sequences in order to attenuate or control an entropy source. Controlling sequences refers to modulated or amplified measurement results from a quantum system that can be used to attenuate the environment of the quantum system.

[0056] In some embodiments, the qudit coherent control system comprises at least one pumping laser that coherently changes or amplifies the states of the qudit components of the quantum register. In some embodiments, the controlled entropy source comprises an array of focused laser beams or electro-optical modulation devices. In some embodiments, each of the qudit components of the quantum register is a single atom, a single ion, or a single photon. In some embodiments, the coherent state transformation is a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the controlled entropy source applies continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state. In some embodiments, each of the qudit components is a qubit that has two quantized states.

[0057] In some embodiments, the quantum information processing system comprises a quantum register comprising an array of qudit components, wherein each qudit componentcomprises at least two quantized states; a qudit coherent control system coupled to the quantum register and configured to exert a coherent state transformation to the qudit components of the quantum register; and a quantum feedback channel coupled to the quantum register, the quantum feedback channel configured to induce controlled loss of information to the qudit components of the quantum register according to the quantum states of the qudit components of the quantum register. A quantum feedback channel is a component of a quantum information processing system that induces controlled loss of information to qudit components of a quantum information processing system. Controlled loss of information refers to intentional and advantageous loss of information in a quantum system in the context of quantum information processing. Controlled loss of information may be dependent on the states of a quantum system. In some embodiments, controlled loss of information may refer to subjecting a composite quantum system of qubits to joint measurement such that the qubits are coupled to a highly dissipative state when the joint quantum state is anything but all of the qubits being in the ground state or all of the qubits being in the excited state. Controlled loss of information may, for example, be used to prepare entangled qubits by advantageous loss of state population (e.g., removal of 101) and 110) states from a 2-qubit superposition to yield a Bell state comprising only 100) and 111) states in the superposition).

[0058] In some embodiments, the qudit coherent control system comprises at least one pumping laser that coherently changes or amplifies states of the qudit components of the quantum register. In some embodiments, each of the qudit components of the quantum register is a single atom, a single ion, or a single photon. In some embodiments, the quantum feedback channel comprises an array of focused laser beams or electro-optical modulation devices. In some embodiments, each of the qudit components is a qubit that has two quantized states.

[0059] Provided herein are methods of operating a quantum information processing system. In some embodiments, the method for operating a quantum information processing system comprises applying a coherent control force to qudit components of a quantum register of the quantum information processing system to dynamically evolve the qudit components; and coupling at least one of the qudit components of the quantum register to a controlled entropy source of the quantum information processing system to apply measurement pulses to the subset of qudit components coupled to the controlled entropy source to alter the coherent dynamics of the qudit components through backactions inducedby quantum measurements. Coherent dynamics of the qudit components refers to dynamics of the qudit components wherein quantum information of the qudit components is not lost. A backaction refers to the effect a detector effectuating a measurement has on the measurement such as, for example, the environment of a quantum system, which effectuates measurement of the quantum system, having a backaction effect on the quantum system. Applying a coherent control force refers to acting upon a quantum system with a coherent state transformation. Dynamic evolution refers to the evolution of a quantum system according to the time-dependent Schrodinger equation, which may be influenced by, for example, an applied potential term or transformation force. A subset of qudit components refers to one or more of the qudit components of the quantum information processing system and may include all of the qudit components of the quantum information processing system. In some embodiments, a subset of qudit components may specifically exclude one or more select qudit components. Measurement pulses refers to any interaction caused to a quantum system to effectuate measurement of the quantum system. In some embodiments, the qudit components are all each initially in a ground state.

[0060] In some embodiments, at least one select qudit component is not coupled to the controlled entropy source, and the method further comprises maintaining the coherent control force and the coupling between the at least one qudit component and the controlled entropy source until the at least one select qudit component is in a desirable state. A desirable state refers to a state of a quantum system that, when occupied by the quantum system, is situationally advantageous in the context of a quantum information processing method. In some embodiments, the coherent control force is a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the controlled entropy source applies continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state.

[0061] In some embodiments, at least two select qudit components are not coupled to the controlled entropy source, and the method further comprises maintaining the coherent control force and the coupling between the at least one qudit component and the controlled entropy source while entangling the at least two select qudit components by subjecting the at least two select qudit components to joint measurement. Joint measurement refers to the coupling of joint quantum states of qudits to an external degree of freedom or to a plurality of external degrees of freedom in a way such that the coupling is dependent on the joint states of thequdits rather than the individual states. In some embodiments, the coherent control force is a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the controlled entropy source applies continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state.

[0062] In some embodiments, a first select qudit component is initially in an arbitrary superposition state and the remainder of the qudit components are initially in the ground state. In some embodiments, the subset of qudit components does not include the first select qudit component and at least one additional select qudit component of the quantum register, and the method further comprises maintaining the coherent control force and the coupling between the at least one qudit component and the controlled entropy source while entangling the first and at least one additional select qudit components by subjecting the first and at least one additional select qudit components to joint measurement. In some embodiments, the coherent control force is a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the controlled entropy source applies continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state. In some embodiments, each of the qudit components is a qubit that has two quantized states.

[0063] In some embodiments, the method for operating a quantum information processing system comprises applying a coherent control force to qudit components of a quantum register of the quantum information processing system to dynamically evolve the qudit components; and coupling at least one of the qudit components of the quantum register to a quantum feedback channel of the quantum information processing system to induce controlled loss of information to the qudit components of the quantum register according to the quantum states of the qudit components of the quantum register. In some embodiments, the qudit components are all each initially in a ground state.

[0064] In some embodiments, at least one select qudit component is not coupled to the quantum feedback channel, and the method further comprises maintaining the coherent control force and the coupling between the at least one qudit component and the quantum feedback channel until the at least one select qudit component is in a desirable state. In some embodiments, the coherent control force is a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state andthe quantum feedback channel applies continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state.

[0065] In some embodiments, at least two select qudit components are not coupled to the quantum feedback channel, and the method further comprises maintaining the coherent control force and the coupling between the at least one qudit component and the quantum feedback channel while entangling the at least two select qudit components by subjecting the at least two select qudit components to joint measurement. In some embodiments, the coherent control force is a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the quantum feedback channel applies continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state.

[0066] In some embodiments, a first select qudit component is initially in an arbitrary superposition state and the remainder of the qudit components are initially in the ground state. In some embodiments, the subset of qudit components does not include the first select qudit component and at least one additional select qudit component of the quantum register, and the method further comprises maintaining the coherent control force and the coupling between the at least one qudit component and the quantum feedback channel while entangling the first and at least one additional select qudit components by subjecting the first and at least one additional select qudit components to joint measurement. In some embodiments, the coherent control force is a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the quantum feedback channel applies continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state. In some embodiments, each of the qudit components is a qubit that has two quantized states.

[0067] The disclosed subject matter relates to apparatus, systems, and methods for quantum data processing based on the coupling of a quantum state with its environment. Such a framework is referred to as entropy quantum computing (EQC). In some embodiments, the systems and methods described herein do not require closed quantum systems and make use of the coupling of a quantum state with its surroundings. In some embodiments, the systems and methods described herein operate in an open quantum system, for example, a quantum computing system including a set of information carrying objects that interact with external degrees of freedom. Its operation is based on the third postulate of quantum mechanics, which states that when a quantum object is measured, its wavefunction collapses to one of theeigenstates of the measurement apparatus. This is a manifestation of quantum backaction, where the interaction of a quantum object with another object or a set of other objects will lead to the change of its quantum state.

[0068] EQC is rooted deeply in this fundamental principle of quantum physics. Instead of trying to prepare an isolated quantum system in pristine quantum states, EQC exposes the quantum system to engineered degrees of freedom in the environment, so that the quantum system can be evolved into certain quantum state(s) that represent the desirable solution of a problem of interest or so that the quantum system contains information that leads to the solution.

[0069] EQC is an approach to quantum data processing that can be generally applied to many different use cases. In one embodiment, by evolving systems with a superposition or a mixture of input states, the system outputs will be in the ground or highest-energy states with near unity probability or to a very good approximation for practical purposes. In another embodiment, by incorporating a system in a feedback configuration, it will quickly reach equilibrium in the ground state.

[0070] Unlike quantum annealing or gate-based techniques, here the system evolution is affected by — sometimes driven by — the environment surrounding the system. As a result, there is no need to prepare or maintain pristine quantum states. This helps to avoid the need for cryogenic and vacuum housing. In many embodiments, the processing can be realized on integrated photonic or electronic platforms, so that the devices are stable, durable, and robust when operating at room temperature and in ambient environment. The same advantages allow for mass production at low cost, offer exceptional scalability and modularity, and provide versatility and reconfigurability by circuit redesigning or reprogramming.

[0071] Many quantum theories and models are based on the assumption of a closed quantum system, whose quantum state can be described by a pure wavefunction. However, this is just an approximation. In reality, any quantum system is coupled to external degrees of freedom, the aggregation of which is often referred to herein as the environment. For example, coupling can be achieved between a charged quantum particle and an external electrical field through a dipole interaction or an atom and background electromagnetic waves through a dipole interaction. Even if a quantum object is placed in a vacuum at nearly absolute zero temperature, it can still be coupled to electromagnetic vacuum because of the inherent quantum vacuum fluctuations. A good example is spontaneous emission, or promptfluorescence where a quantum emitter decays to a lower energy state by emitting an optical or microwave photon, typically with a lifetime measured in nanoseconds.

[0072] It is impossible to totally isolate a quantum state from its surroundings. Suppressing its coupling with the environment can be done to some extent, but at the price of large system overhead and / or operational costs. For example, isolating an ion array requires placing the ion array in a nearly perfect vacuum close to the absolute zero temperature. To isolate superconductor qubits, one needs to further minimize the electromagnetic background to be nearly zero.

[0073] The systems and methods described herein do not require isolating the information-carrying quantum system from its surroundings entirely. Rather, systems and methods described herein include quantum open systems that can include coupling between the quantum system and its environment. FIG. 1 illustrates an example of a quantum open system, which includes the quantum system, the surrounding environment, and their interaction. The quantum open system can be modelled by a composite Hamiltonian Htotaicontaining three parts: totai HSyS+ Henv+ Hint:

[0074] where Hsysis the Hamiltonian describing the dynamics exclusive to the quantum system, Henvis the Hamiltonian describing the dynamics exclusive to the environment, and Hintcaptures the coupling between the system and environment.

[0075] Depending on the relative dynamical time scales of the three Hamiltonians, as well as the degrees of freedom contained in the environment, the quantum open system can be in a Markovian and non-Markovian regime. In the former case, the interaction occurs at a rate much faster than the system evolution and the environment contains many degrees of freedom with a flat spectrum, so that it can revert back to equilibrium in practically no time after such interaction occurs. In the latter case, the environment has a finite response and relaxation time, so that it contains some memories for prior interaction. The backaction on the system in these two cases can be very different.

[0076] When the coupling is non-zero, the system’s quantum state is not pure and usually cannot be described by a single wavefunction. Instead, it is an admixture of states described by a density matrix, which is essentially a statistical mixture of different pure states.

[0077] The systems and methods described herein can make use of the backaction of the environment on the quantum system to force the system to evolve into a desirable state. Described below are three ways to achieve this end.

[0078] A first way to make use of the backaction of the environment on the quantum system to force the system to evolve into a desirable state includes modifying the spectrum of the environment, which in the time domain, includes changing the response time and behavior of the environment. This can be achieved by changing Henv. In some embodiments, the environment can be made time dependent by introducing a time-dependent Hamiltonian Henv= Henv(t). Alternatively, changing Henvcan be achieved by introducing non-flat spectral responses, such as wavelength-dependent losses in the case of an electromagnetic environment. FIG. 2 shows an example of how such a time-dependent environment can be constructed around a quantum particle. The time-dependent environment is formed by two mirrors around the particle, so that a photon emitted from the particle can be reflected from the mirrors and stay with the particle for some time. This is a typical realization of cavity quantum electrodynamics, where the environment is no longer “white” (e.g., “Markovian”) and thus has a finite memory time (e.g., “non-Markovian”). As a result, the particle’s dynamics can be affected, resulting in suppression of spontaneous emissions, enhanced dipole coupling with photons, etc. By replacing the right-hand side mirror with a switch mirror whose reflectance can be turned on and off quickly, the environment is now time dependent. As such, the quantum particle’s dynamics will be affected. By applying a proper on / off time sequence, it is possible to force the particle to evolve into a certain quantum state of user definition.

[0079] FIG. 3 is another example of an engineered environment, where instead of using a time-dependent Hamiltonian, an absorptive material is inserted into the cavity with a certain uneven absorption spectrum. As such, the environment’s property is engineered, and the particle’s quantum dynamics will be affected.

[0080] A second way to make use of the backaction of the environment on the quantum system to force the system to evolve into a desirable state includes changing the interaction Hamiltonian Hint. In some embodiments, the interaction can be made stronger to allow fast relaxation. In some embodiments, the interaction can be made weaker, to carefully sample many closely-spaced, pseudo-degenerate quantum energy levels. In some embodiments, the interaction can be made time dependent, so that the system can be guided to evolve into a certain quantum state of interest.

[0081] FIG. 4 shows an example of how the interaction of a particle with vacuum fluctuations can be controlled. There are three energy levels of relevance in this example, the ground state, excited state, and metastable state. A quantum particle interacts with the vacuum through spontaneous emission from the excited state. To turn off such interaction, one can use a Rabi pulse to pump the atom from the excited state to the metastable state, where the system can stay there for a long time, relative to the original excited state lifetime, without decaying.

[0082] A third way to make use of the backaction of the environment on the quantum system to force the system to evolve into a desirable state includes a combination of both of the prior two approaches above and includes augmenting both the environment and the coupling between the quantum system and the environment simultaneously. Such an approach can circumvent the difficulties in precisely controlling either aspect while allowing greater flexibilities in designing and implementing the algorithm.

[0083] In some embodiments, the systems and methods described herein realize quantum data processing through the quantum Zeno effect, by which quantum states of the objective quantum system are forced to evolve into a decoherence subspace due to the partial collapse of the wavefunction. Despite the widely held belief that decoherence must always be avoided in quantum-information processing, it has been known for some time that decoherence can instead be harnessed to implement high-efficiency coherent quantum logic gates for single photons and atoms. These gates rely on the fact that strong coupling to the environment is equivalent to continuous measurement, and can therefore inhibit coherent quantum dynamics, in analogy with the quantum Zeno effect. To best understand how such an effect can lead to coherent entanglement generation, consider a set of experiments where the Zeno effect was used to allow a single photon to image an absorbing object without being absorbed, known as high-efficiency interaction-free measurement (IFM), or alternatively as “quantum interrogation.” Replacing the classical absorber with an atomic qubit, prepared in a superposition of absorbing and transparent states, can coherently change the quantum state of the probe photon conditioned on the state of the atomic qubit. This leads to atom-photon entanglement, generated via a mechanism in which the atom and photon arguably never interact directly, so that spontaneous emission decoherence is avoided even for a resonant photon. In such a system it is simply the possibility of a strong dissipative interaction which drives the Zeno effect and creates entanglement, without dissipation actually occurring

[0084] FIG. 5 illustrates an example of how the systems and methods described herein may use quantum Zeno effects to control the output of a multiport circuit for quantum state transformation. The multiport circuit for a quantum state transformation includes five inputs and five outputs, said inputs and outputs being connected by five waveguides that are evanescently coupled. As shown in FIG. 5 (left panel), under a normal operation, an input state will be transformed to an output state according to a transformation matrix, which in the context of FIG. 5 is a 5x5 matrix with non-zero off-diagonal elements. A quantum state in |1) at the input could become a superposition state of { 11'), 12' ), |3'), |4'), 15' )}, and vice versa. However, if strong loss is introduced to waveguide 3 (the middle waveguide), as shown in FIG. 5 (right panel), the coupling of the quantum state to the environment becomes uneven for each waveguide. As such, waveguide 3 will become decoupled from the other waveguides, and the transform matrix will be very different. In fact, if the loss occurs at a rate much higher than that of evanescent coupling, particles in waveguide 1 and 2 will not be able to couple over to waveguide 4 and 5, and vice versa. The quantum dynamics can be controlled by switching on and off the loss for waveguide 3. For example, electric or acoustic signals can be employed to augment the loss of waveguide 3 through electro-optical or acousto-optical effects.

[0085] FIG. 6 illustrates an example of how an engineered environment, according to the systems and methods described herein, can achieve a logical operation between two quantum objects by an engineered environment. As shown in FIG. 6 (left panel), object A is trapped in a double-well potential with left and right wells separated by a low energy barrier that allows efficient tunneling between the two. Initially in the left well, A can tunnel to the right well. However, as shown in FIG. 6 (right panel), if there is another object B in the right well that will annihilate A, A will not tunnel to the right well, because the coherence between the two wells — as needed for the tunneling — would be reduced so that the tunneling is suppressed. In this way, B controls the quantum state of A, which can be exploited to construct logical operations between the two, including quantum C-NOT gate, controlled-phase gate, etc.

[0086] A significant advantage of the systems and methods described herein is that the quantum system can be evolved into a stable quantum state, which is largely immune to decoherence and noise. Such stability will allow operation over long time and with many particles, as needed to solve realistic problems.

[0087] It will be understood that the embodiments described herein are merely illustrative and exemplary and that a person skilled in the art may make many variations andmodifications without departing from the spirit and scope of the claimed subject matter. Also, the same technologies can be applied to a wide range of material systems, including those of photonics, atoms, radio-frequency waves, ions, where EQC Hamiltonians can be constructed following the similar design approaches. All such variations, extensions, and modifications are intended to be included within the scope of the disclosure.I. Exemplary Systems

[0088] FIG. 7A is a block diagram of an exemplary quantum information processing system 700. Quantum information processing system 700 may include various components, including quantum register 710, qudit coherent control system 720, and controlled entropy source 730. In some embodiments, quantum register 710 may include, for example, a plurality of qudit components. For example, a quidit component can be a single atom, a single ion, or a single photon. In some embodiments, qudit coherent control system 720 is coupled to quantum register 710. In some embodiments, qudit coherent control system 720 is configured to exert a coherent state transformation to the qudit components of quantum register 710. In some embodiments, controlled entropy source 730 is configured to couple to the qudit components of quantum register 710 to apply continuous or periodic measurement to the qudit components of quantum register 710 that are coupled to controlled entropy source 730.

[0089] In some embodiments, the quantum information processing system illustrated in FIG. 7 A may be further understood by the illustration of FIG. 7B. As shown in the block diagram of FIG. 7B, quantum register 710 may include, for example, an array of qudit components 712. The array of qudit components 712 may include a plurality of qudit components 712a-712d. While four qudit components are explicitly included in FIG. 7B, this is merely exemplary and it will be understood to a person of ordinary skill that any number of qudit components can be used, including, for example, as few as ten, one hundred, one thousand, or one million qudit components. In some embodiments, qudit coherent control system 720 is coupled to qudit components of qudit array 712. In some embodiments, qudit coherent control system 720 is configured to exert a coherent state transformation to the qudit components of qudit array 712. In some embodiments, controlled entropy source 730 is configured to couple to qudit components of qudit array 712. In some embodiments, the qudit components of qudit array 712 are each a single atom. In some embodiments, the qudit components of qudit array 712 are each a single ion. In some embodiments, the qudit components of qudit array 712 are each a single photon. In some embodiments, the quditcomponents each comprise at least two quantized states. In some embodiments, the qudit components are each a qubit that has only two quantized states.

[0090] In some embodiments, the quantum information processing system illustrated in FIG. 7B may be further understood by the illustration of FIG. 7C. As shown in the block diagram of FIG. 7C, qudit coherent control system 720 may include, for example, at least one pumping laser 722. The at least one pumping laser 722 may include, for example, a plurality of pumping lasers 722a-722d. While four pumping lasers are explicitly included in FIG. 7C, this is merely exemplary and it will be understood to a person of ordinary skill that any number of pumping lasers can be used, including, for example, as few as ten, one hundred, or one thousand pumping lasers. In some embodiments, a single pumping laser comprising a plurality of frequency comb lines is used, with each frequency comb line addressing one or a plurality of qudit components. In some embodiments, the at least one pumping laser 722 is coupled to qudit components of qudit array 712. In some embodiments, the at least one pumping laser 722 is configured to exert a coherent state transformation to the qudit components of qudit array 712 to coherently change the states of the qudit components of qudit array 712.

[0091] In some embodiments, the quantum information processing system illustrated in FIG. 7C may be further understood by the illustration of FIG. 7D. As shown in the block diagram of FIG. 7D, controlled entropy source 730 may include, for example, an array of electro-optical modulation (EOM) devices 732. The array of EOM devices 732 may include a plurality of EOM devices 732a-732d. While four EOM devices are explicitly included in FIG. 7D, this is merely exemplary and it will be understood to a person of ordinary skill that any number of EOM devices can be used, including, for example, as few as ten, one hundred, or one thousand EOM devices, especially in particular embodiments employing nanophotonic chip devices. Controlled entropy source 730 may include, for example, an array of focused laser beams 734. Array of focused laser beams 734 may include, for example, a plurality of focused laser beams 734a-734d. While four focused laser beams are explicitly included in FIG. 7D, this is merely exemplary and it will be understood to a person of ordinary skill that any number of focused laser beams can be used, including, for example, as few as ten, one hundred, or one thousand focused laser beams. In some embodiments, the array of EOM devices 732 is configured to couple to the qudit components of qudit array 712. In some embodiments, the array of EOM devices 732 is configured to apply continuous or periodic measurement to the qudit components of qudit array 712. In some embodiments, the array ofEOM devices 732 introduces differential losses to different qudit components of qudit array 712. In some embodiments, the array of focused laser beams 734 is configured to couple to the qudit components of qudit array 712. In some embodiments, the array of focused laser beams 734 is configured to apply continuous or periodic measurement to the qudit components of qudit array 712.

[0092] In various embodiments, the qudit coherent control system 720 of the block diagrams of FIGs. 7A-7D is configured to exert a coherent state transformation that is a rotation force uniformly applied to the qudit components of quantum register 710 to simultaneously transition each of the qudit components to an excited state and controlled entropy source 730 of the block diagrams of FIGs. 7A-7D applies continuous measurement to the qudit components of quantum register 710 at a greater rate than the rotation force uniformly applied to the qudit components can transition the qudit components to the excited state.

[0093] In some embodiments, the quantum information processing system illustrated in FIG. 7 A may be further understood by the illustration of FIG. 7E. As shown in the block diagram of FIG. 7E, quantum information processing system 700 may include, for example, feedback control unit 740 and quantum measurement port 750. In some embodiments, quantum register 710 may include, for example, a plurality of qudit components. In some embodiments, feedback control unit 740 couples the quantum measurement port and the controlled entropy source. In some embodiments, feedback control unit 740 is configured to generate controlling sequences from the measurement results received by quantum measurement port 750 to control controlled entropy source 730. In some embodiments, feedback control unit 740 is configured to generate controlling sequences from the measurement results received by quantum measurement port 750 to modulate the coupling of qudit components of quantum register 710 to the controlled entropy source 730. In some embodiments, quantum measurement port 750 is configured to receive measurement results from the qudit components of quantum register 710.

[0094] In some embodiments, the quantum information processing system illustrated in FIG. 7E may be further understood by the illustration of FIG. 7F. As shown in the block diagram of FIG. 7F, quantum register 710 may include, for example, an array of qudit components 712. The array of qudit components 712 may include a plurality of qudit components 712a-712d. While four qudit components are explicitly included in FIG. 7F, this is merely exemplary and it will be understood to a person of ordinary skill that any number ofqudit components can be used, including, for example, as few as ten, one hundred, one thousand, or one million qudit components. In some embodiments, qudit coherent control system 720 is coupled to qudit components of qudit array 712. In some embodiments, qudit coherent control system 720 is configured to exert a coherent state transformation to the qudit components of qudit array 712. In some embodiments, controlled entropy source 730 is configured to couple to qudit components of qudit array 712. In some embodiments, quantum measurement port 750 is configured to couple to the qudit components of qudit array 712. In some embodiments, quantum measurement port 750 is configured to receive measurement results from the qudit components of qudit array 712. In some embodiments, the qudit components of qudit array 712 are each a single atom. In some embodiments, the qudit components of qudit array 712 are each a single ion. In some embodiments, the qudit components of qudit array 712 are each as single photon. In some embodiments, the qudit components of qudit array 712 each comprise at least two quantized states. In some embodiments, the qudit components of qudit array 712 are each a qubit that has only two quantized states.

[0095] In some embodiments, the quantum information processing system illustrated in FIG. 7F may be further understood by the illustration of FIG. 7G. As shown in the block diagram of FIG. 7G, qudit coherent control system 720 may include, for example, at least one pumping laser 722. The at least one pumping laser 722 may include a plurality of pumping lasers 722a-722d. While four pumping lasers are explicitly included in FIG. 7G, this is merely exemplary and it will be understood to a person of ordinary skill that any number of pumping lasers can be used, including, for example, as few as ten, one hundred, or one thousand pumping lasers. In some embodiments, a single pumping laser comprising a plurality of frequency comb lines is used, with each frequency comb line addressing one or a plurality of qudit components. In some embodiments, the at least one pumping laser is coupled to qudit components of qudit array 712. In some embodiments, the at least one pumping laser 722 is configured to exert a coherent state transformation to the qudit components of qudit array 712 to coherently change the states of the qudit components of qudit array 712.

[0096] In some embodiments, the quantum information processing system illustrated in FIG. 7G may be further understood by the illustration of FIG. 7H. As shown in the block diagram of FIG. 7H, controlled entropy source 730 may include, for example, an array of electro-optical modulation (EOM) devices 732. The array of EOM devices 732 may include aplurality of EOM devices 732a-732d. While four EOM devices are explicitly included in FIG. 7H, this is merely exemplary and it will be understood to a person of ordinary skill that any number of EOM devices can be used, including, for example, as few as ten, one hundred, or one thousand EOM devices, especially in particular embodiments employing nanophotonic chip devices. Controlled entropy source 730 may include, for example, an array of focused laser beams 734. Array of focused laser beams 734 may include, for example, a plurality of focused laser beams 734a-734d. While four focused laser beams are explicitly included in FIG. 7H, this is merely exemplary and it will be understood to a person of ordinary skill that any number of focused laser beams can be used, including, for example, as few as ten, one hundred, or one thousand focused laser beams. In some embodiments, the array of EOM devices 732 is configured to couple to the qudit components of qudit array 712. In some embodiments, the array of EOM devices 732 is configured to apply continuous or periodic measurement to the qudit components of qudit array 712. In some embodiments, the array of EOM devices 732 introduces differential losses to different qudit components of qudit array 712. In some embodiments, the array of focused laser beams 734 is configured to couple to the qudit components of qudit array 712. In some embodiments, the array of focused laser beams 734 is configured to apply continuous or periodic measurement to the qudit components of qudit array 712. In some embodiments, feedback control unit 740 is configured to couple to the array of EOM devices 732. In some embodiments, feedback control unit 740 is configured to couple to the array of focused laser beams 734. In some embodiments, feedback control unit 740 is configured to generate controlling sequences from the measurement results received by quantum measurement port 750 to control controlled entropy source 730. In some embodiments, feedback control unit 740 is configured to generate controlling sequences from the measurement results received by quantum measurement port 750 to modulate the coupling of the qudit components of qudit array 712 to controlled entropy source 730.

[0097] In various embodiments, the qudit coherent control system of the block diagrams of FIGs. 7F-7H is configured to exert a coherent state transformation that is a rotation force uniformly applied to the qudit components of quantum register 710 to simultaneously transition each of the qudit components to an excited state and controlled entropy source 730 of the block diagrams of FIGs. 7F-7H applies continuous measurement to the qudit components of quantum register 710 at a greater rate than the rotation force uniformly applied to the qudit components can transition the qudit components to the excited state.

[0098] FIG. 8A is a block diagram of an exemplary quantum information processing system 800. Quantum information processing system 800 may include various components, for example, quantum register 810, qudit coherent control system 820, and quantum feedback channel 830. In some embodiments, quantum register 810 may include, for example, a plurality of qudit components. In some embodiments, the qudit components of quantum register 810 are each a single atom. In some embodiments, the qudit components of quantum register 810 are each a single ion. In some embodiments, the qudit components of quantum register 810 are each a single photon. In some embodiments, qudit coherent control system 820 is coupled to quantum register 810. In some embodiments, qudit coherent control system 820 is configured to exert a coherent state transformation to the qudit components of quantum register 810. In some embodiments, quantum feedback channel 830 is coupled to quantum register 810. In some embodiments, quantum feedback channel 830 is configured to induce controlled loss of information to the qudit components of quantum register 810 according to the quantum states of the qudit components of quantum register 810.

[0099] In some embodiments, the quantum information processing system illustrated in FIG. 8 A may be further understood by the illustration of FIG. 8B. As shown in the block diagram of FIG. 8B, quantum register 810 may include, for example, an array of qudit components 812. The array of qudit components 812 may include a plurality of qudit components 812a-812d. While four qudit components are explicitly included in FIG. 8B, this is merely exemplary and it will be understood to a person of ordinary skill that any number of qudit components can be used, including, for example, as few as ten, one hundred, one thousand, or one million qudit components. In some embodiments, qudit coherent control system 820 is coupled to qudit components of qudit array 812. In some embodiments, qudit coherent control system 820 is configured to exert a coherent state transformation to the qudit components of qudit array 812. In some embodiments, quantum feedback channel 830 is configured to couple to qudit components of qudit array 812. In some embodiments, the qudit components of qudit array 812 are each a single atom. In some embodiments, the qudit components of qudit array 812 are each a single ion. In some embodiments, the qudit components of qudit array 812 are each a single photon. In some embodiments, the qudit components each comprise at least two quantized states. In some embodiments, the qudit components are each a qubit that has only two quantized states.

[0100] In some embodiments, the quantum information processing system illustrated in FIG. 8B may be further understood by the illustration of FIG. 8C. As shown in the blockdiagram of FIG. 8C, qudit coherent control system 820 may include, for example, at least one pumping laser 822. The at least one pumping laser 822 may include, for example, a plurality of pumping lasers 822a-822d. While four pumping lasers are explicitly included in FIG. 8C, this is merely exemplary and it will be understood to a person of ordinary skill that any number of pumping lasers can be used, including, for example, as few as ten, one hundred, or one thousand pumping lasers. In some embodiments, a single pumping laser comprising a plurality of frequency comb lines is used, with each frequency comb line addressing one or a plurality of qudit components. In some embodiments, the at least one pumping laser 822 is coupled to qudit components of qudit array 812. In some embodiments, the at least one pumping laser 822 is configured to exert a coherent state transformation to the qudit components of qudit array 812 to coherently change or amplify the states of the qudit components of qudit array 812.

[0101] In some embodiments, the quantum information processing system illustrated in FIG. 8C may be further understood by the illustration of FIG. 8D. As shown in the block diagram of FIG. 8D, quantum feedback channel 830 may include, for example, an array of electro-optical modulation (EOM) devices 832. The array of EOM devices 832 may include a plurality of EOM devices 832a-832d. While four EOM devices are explicitly included in FIG. 8D, this is merely exemplary and it will be understood to a person of ordinary skill that any number of EOM devices can be used, including, for example, as few as ten, one hundred, or one thousand EOM devices, especially in particular embodiments employing nanophotonic chip devices. Quantum feedback channel 830 may include, for example, an array of focused laser beams 834. Array of focused laser beams 834 may include, for example, a plurality of focused laser beams 834a-834d. While four focused laser beams are explicitly included in FIG. 8D, this is merely exemplary and it will be understood to a person of ordinary skill that any number of focused laser beams can be used, including, for example, as few as ten, one hundred, or one thousand focused laser beams. In some embodiments, the array of EOM devices 832 is configured to couple to the qudit components of qudit array 812. In some embodiments, the array of EOM devices 832 is configured to induce controlled loss of information to the qudit components of qudit array 812 according to the quantum states of the qudit components of qudit array 812. In some embodiments, the array of focused laser beams 834 is configured to couple to the qudit components of qudit array 812. In some embodiments, the array of focused laser beams 834 is configured to induce controlled loss ofinformation to the qudit components of qudit array 812 according to the quantum states of the qudit components of qudit array 812.II. Exemplary Methods

[0102] FIG. 9 illustrates a flow diagram 900 of a method for operating a quantum information processing system in accordance with the presently disclosed embodiments. The flow diagram 900 may be performed utilizing one or more quantum information processing systems (e.g., quantum information processing system 700 as discussed above with respect to FIGs. 7A-7H). The flow diagram 900 may begin at block 902 with applying a coherent control force to qudit components of a quantum register of a quantum information processing system to dynamically evolve the qudit components. The flow diagram 900 may then conclude at block 904 with coupling at least one of the qudit components of the quantum register to a controlled entropy source to apply measurement pulses to the subset of qudit components that are coupled to the controlled entropy source to alter the coherent dynamics of the qudit components through backactions induced by quantum measurements.

[0103] FIG. 10 illustrates a flow diagram 1000 of a method for operating a quantum information processing system in accordance with the presently disclosed embodiments. The flow diagram 1000 may be performed utilizing one or more quantum information processing systems (e.g., quantum information processing system 700 as discussed above with respect to FIGs. 7A-7H). The flow diagram 1000 may begin at block 1002 with qudit components of a quantum register of a quantum information processing system each all initially in the ground state. The flow diagram 1000 may then continue at block 1004 with applying a coherent control force to the qudit components of the quantum register to dynamically evolve the qudit components. The flow diagram 1000 may then conclude at block 1006 with coupling at least one of the qudit components of the quantum register to a controlled entropy source to apply measurement pulses to the subset of qudit components that are coupled to the controlled entropy source to alter the coherent dynamics of the qudit components through backactions induced by quantum measurements.

[0104] FIG. 11 illustrates a flow diagram 1100 of a method for operating a quantum information processing system in accordance with the presently disclosed embodiments. The flow diagram 1100 may be performed utilizing one or more quantum information processing systems (e.g., quantum information processing system 700 as discussed above with respect to FIGs. 7A-7H). The flow diagram 1100 may begin at block 1102 with qudit components of aquantum register of a quantum information processing system each all initially in the ground state. The flow diagram 1100 may then continue at block 1104 with applying a coherent control force to the qudit components of the quantum register to dynamically evolve the qudit components. The flow diagram 1100 may then continue at block 1106 with coupling at least one of the qudit components of the quantum register to a controlled entropy source, wherein at least one select qudit component is not coupled to the controlled entropy source. The flow diagram 1100 may then conclude at block 1108 with maintaining the coherent control force of block 1104 and maintaining the coupling between a controlled entropy source and qudit components of block 1106 until the at least one select non-coupled qudit component of block 1106 is in a desirable state.

[0105] FIG. 12 illustrates a flow diagram 1200 of a method for operating a quantum information processing system in accordance with the presently disclosed embodiments. The flow diagram 1200 may be performed utilizing one or more quantum information processing systems (e.g., quantum information processing system 700 as discussed above with respect to FIGs. 7A-7H). The flow diagram 1200 may begin at block 1202 with qudit components of a quantum register of a quantum information processing system each all initially in the ground state. The flow diagram 1200 may then continue at block 1204 with applying a coherent control force to the qudit components of the quantum register to dynamically evolve the qudit components. The flow diagram 1200 may then continue at block 1206 with coupling at least one of the qudit components of the quantum register to a controlled entropy source, wherein at least two select qudit components are not coupled to the controlled entropy source. The flow diagram 1200 may then conclude at block 1208 with maintaining the coherent control force of block 1204, maintaining the coupling between a controlled entropy source and qudit components of block 1206, and entangling the at least two select non-coupled qudit components of block 1206 by subjecting the at least two select non-coupled qudit components to joint measurement.

[0106] FIG. 13 illustrates a flow diagram 1300 of a method for operating a quantum information processing system in accordance with the presently disclosed embodiments. The flow diagram 1300 may be performed utilizing one or more quantum information processing systems (e.g., quantum information processing system 700 as discussed above with respect to FIGs. 7A-7H). The flow diagram 1300 may begin at block 1302 with qudit components of a quantum register of a quantum information processing system each all initially in the ground state, except for a first select qudit component that is initially in an arbitrary superpositionstate. The flow diagram 1300 may then continue at block 1304 with applying a coherent control force to the qudit components of the quantum register to dynamically evolve the qudit components. The flow diagram 1300 may then conclude at block 1306 with coupling at least one of the qudit components of the quantum register to a controlled entropy source, wherein the subset of qudit components that are coupled to the controlled entropy source does not include the first select qudit component.

[0107] FIG. 14 illustrates a flow diagram 1400 of a method for operating a quantum information processing system in accordance with the presently disclosed embodiments. The flow diagram 1400 may be performed utilizing one or more quantum information processing systems (e.g., quantum information processing system 700 as discussed above with respect to FIGs. 7A-7H). The flow diagram 1400 may begin at block 1402 with qudit components of a quantum register of a quantum information processing system each all initially in the ground state, except for a first select qudit component that is initially in an arbitrary superposition state. The flow diagram 1400 may then continue at block 1404 with applying a coherent control force to the qudit components of the quantum register to dynamically evolve the qudit components. The flow diagram 1400 may then continue at block 1406 with coupling at least one of the qudit components of the quantum register to a controlled entropy source, wherein the subset of qudit components that are coupled to the controlled entropy source does not include the first select qudit component and at least one additional select qudit component. The flow diagram 1400 may then conclude at block 1408 with maintaining the coherent control force of block 1404, maintaining the coupling between a controlled entropy source and qudit components of block 1406, and entangling the first select qudit component and at least one additional select qudit component by subjecting the select non-coupled qudit components to joint measurement.

[0108] The flow diagrams 900, 1000, 1100, 1200, 1300, and 1400 may be performed utilizing one or more quantum information processing systems (e.g., quantum information processing system 700 as discussed above with respect to FIGs. 7A-7H) that may include a quantum register (e.g., quantum register 710 as discussed above with respect to FIGs. 7A- 7H), a qudit coherent control system (e.g., qudit coherent control system 720 as discussed above with respect to FIGs. 7A-7H), a controlled entropy source (e.g., controlled entropy source 730 as discussed above with respect to FIGs. 7A-7H), a feedback control unit (e.g., feedback control unit 740 as discussed above with respect to FIGs. 7E-7H), a quantum measurement port (e.g., quantum measurement port 750 as discussed above with respect toFIGs. 7E-7H), or a combination thereof in accordance with the presently disclosed embodiments. In some embodiments, the quantum register may include, for example, a qudit array (e.g., qudit array 712 as discussed above with respect to FIGs. 7B-7D and FIGs. 7F- 7H). In some embodiments, the qudit array may include, for example, a plurality of qudit components (e.g., qudit components 712a-712d as discussed above with respect to FIGs. 7B- 7D and FIGs. 7F-7H). In some embodiments, the qudit coherent control system may include, for example, at least one pumping laser (e.g., at least one pumping laser 722 as discussed above with respect to FIGs. 7C-7D and 7G-7H). In some embodiments, the at least one pumping laser may include, for example, a plurality of pumping lasers (e.g., pumping lasers 722a-722d as discussed above with respect to FIGs. 7C-7D and 7G-7H). In some embodiments, the controlled entropy source may include, for example, an array of electro- optical modulation (EOM) devices (e.g., array of EOM devices 732 as discussed above with respect to FIGs. 7D and 7G). In some embodiments, the array of EOM devices may include, for example, a plurality of EOM devices (e.g., EOM devices 732a-732d as discussed above with respect to FIGs. 7D and 7G). In some embodiments, the controlled entropy source may include, for example, an array of focused laser beams (e.g., array of focused laser beams 734 as discussed above with respect to FIGs. 7D and 7G). In some embodiments, the array of focused laser beams may include, for example, a plurality of focused laser beams (e.g., focused laser beams 734a-734d as discussed above with respect to FIGs. 7D and 7G).

[0109] In some embodiments, the coherent control force of flow diagrams 900, 1000, 1100, 1200, 1300, and 1400 is a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the controlled entropy source applies continuous measurement to the qudit components that are coupled to the controlled entropy source at a greater rate than the rotation force can transition the qudit components to the excited state. In some embodiments, each of the qudit components of flow diagrams 900, 1000, 1100, 1200, 1300, and 1400 is a qubit that has two quantized states.

[0110] FIG. 15 illustrates a flow diagram 1500 of a method for operating a quantum information processing system in accordance with the presently disclosed embodiments. The flow diagram 1500 may be performed utilizing one or more quantum information processing systems (e.g., quantum information processing system 800 as discussed above with respect to FIGs. 8A-8D). The flow diagram 1500 may begin at block 1502 with applying a coherent control force to qudit components of a quantum register of a quantum information processing system to dynamically evolve the qudit components. The flow diagram 1500 may thenconclude at block 1504 with coupling at least one of the qudit components of the quantum register to a quantum feedback channel to induce controlled loss of information to the qudit components of the quantum register according to the quantum states of the qudit components of the quantum register.[OHl] FIG. 16 illustrates a flow diagram 1600 of a method for operating a quantum information processing system in accordance with the presently disclosed embodiments. The flow diagram 1600 may be performed utilizing one or more quantum information processing systems (e.g., quantum information processing system 800 as discussed above with respect to FIGs. 8A-8D). The flow diagram 1600 may begin at block 1602 with qudit components of a quantum register of a quantum information processing system each all initially in the ground state. The flow diagram 1600 may then continue at block 1604 with applying a coherent control force to the qudit components of the quantum register to dynamically evolve the qudit components. The flow diagram 1600 may then conclude at block 1606 with coupling at least one of the qudit components of the quantum register to a quantum feedback channel to induce controlled loss of information to the qudit components of the quantum register according to the quantum states of the qudit components of the quantum register.

[0112] FIG. 17 illustrates a flow diagram 1700 of a method for operating a quantum information processing system in accordance with the presently disclosed embodiments. The flow diagram 1700 may be performed utilizing one or more quantum information processing systems (e.g., quantum information processing system 800 as discussed above with respect to FIGs. 8A-8D). The flow diagram 1700 may begin at block 1702 with qudit components of a quantum register of a quantum information processing system each all initially in the ground state. The flow diagram 1700 may then continue at block 1704 with applying a coherent control force to the qudit components of the quantum register to dynamically evolve the qudit components. The flow diagram 1700 may then continue at block 1706 with coupling at least one of the qudit components of the quantum register to a quantum feedback channel, wherein at least one select qudit components is not coupled to the quantum feedback channel. The flow diagram 1704 may then conclude at block 1708 with maintaining the coherent control force of block 1704 and maintaining the coupling between a quantum feedback channel and qudit components of block 1706 until the at least one select non-coupled qudit component of block 1706 is in a desirable state.

[0113] FIG. 18 illustrates a flow diagram 1800 of a method for operating a quantum information processing system in accordance with the presently disclosed embodiments. Theflow diagram 1800 may be performed utilizing one or more quantum information processing systems (e.g., quantum information processing system 800 as discussed above with respect to FIGs. 8A-8D). The flow diagram 1800 may begin at block 1802 with qudit components of a quantum register of a quantum information processing system each all initially in the ground state. The flow diagram 1800 may then continue at block 1804 with applying a coherent control force to the qudit components of the quantum register to dynamically evolve the qudit components. The flow diagram 1800 may then continue at block 1806 with coupling at least one of the qudit components of the quantum register to a quantum feedback channel, wherein at least two select qudit components are not coupled to the quantum feedback channel. The flow diagram 1800 may then conclude at block 1808 with maintaining the coherent control force of block 1804, maintaining the coupling between a quantum feedback channel and qudit components of block 1806, and entangling the at least two select non-coupled qudit components of block 1806 by subjecting the at least two select non-coupled qudit components to joint measurement.

[0114] FIG. 19 illustrates a flow diagram 1900 of a method for operating a quantum information processing system in accordance with the presently disclosed embodiments. The flow diagram 1900 may be performed utilizing one or more quantum information processing systems (e.g., quantum information processing system 800 as discussed above with respect to FIGs. 8A-8D). The flow diagram 1900 may begin at block 1902 with qudit components of a quantum information processing system each all initially in the ground state, except for a first select qudit component that is initially in an arbitrary superposition state. The flow diagram 1900 may then continue at block 1904 with applying a coherent control force to the qudit components of the quantum register to dynamically evolve the qudit components. The flow diagram 1900 may then conclude at block 1906 with coupling at least one of the qudit components of the quantum register to a quantum feedback channel, wherein the subset of qudit components that are coupled to the quantum feedback channel does not include the first select qudit component.

[0115] FIG. 20 illustrates a flow diagram 2000 of a method for operating a quantum information processing system in accordance with the presently disclosed embodiments. The flow diagram 2000 may be performed utilizing one or more quantum information processing systems (e.g., quantum information processing system 800 as discussed above with respect to FIGs. 8A-8D). The flow diagram 2000 may begin at block 2002 with qudit components of a quantum register of a quantum information processing system each all initially in the groundstate, except for a first select qudit component that is initially in an arbitrary superposition state. The flow diagram 2000 may then continue at block 2004 with applying a coherent control force to the qudit components of the quantum register to dynamically evolve the qudit components. The flow diagram 2000 may then continue at block 2006 with coupling at least one of the qudit components of the quantum register to a quantum feedback channel, wherein the subset of qudit components that are coupled to the quantum feedback channel does not include the first select qudit component and at least one additional select qudit component. The flow diagram 2000 may then conclude at block 2008 with maintaining the coherent control force of block 2004, maintaining the coupling between a quantum feedback channel and qudit components of block 2006, and entangling the first select qudit component and the at least one additional select qudit component by subjecting the select non-coupled qudit components to joint measurement.

[0116] The flow diagrams 1500, 1600, 1700, 1800, 1900, and 2000 may be performed utilizing one or more quantum information processing systems (e.g., quantum information processing system 800 as discussed above with respect to FIGs. 8A-8D) that may include a quantum register (e.g., quantum register 810 as discussed above with respect to FIGs. 8A- 8D), a qudit coherent control system (e.g., qudit coherent control system 820 as discussed above with respect to FIGs. 8A-8D), a quantum feedback channel (e.g., quantum feedback channel 830 as discussed above with respect to FIGs. 8A-8D), or a combination thereof in accordance with the presently disclosed embodiments. In some embodiments, the quantum register may include, for example, a qudit array (e.g., qudit array 812 as discussed above with respect to FIGs. 8B-8D). In some embodiments, the qudit array may include, for example, a plurality of qudit components (e.g., qudit components 812a-812d as discussed above with respect to FIGs. 8B-8D). In some embodiments, the qudit coherent control system may include, for example, at least one pumping laser (e.g., at least one pumping laser 822 as discussed above with respect to FIGs. 8C-8D). In some embodiments, the at least one pumping laser may include, for example, a plurality of pumping lasers (e.g., pumping lasers 822a-822d as discussed above with respect to FIGs. 8C-8D). In some embodiments, the quantum feedback channel may include, for example, an array of electro-optical modulation (EOM) devices (e.g., array of EOM devices 832 as discussed above with respect to FIG. 8D). In some embodiments, the array of EOM devices may include, for example, a plurality of EOM devices (e.g., EOM devices 832a-832d as discussed above with respect to FIG. 8D). In some embodiments, the quantum feedback channel may include, for example, an array offocused laser beams (e.g., array of focused laser beams 834 as discussed above with respect to FIG. 8D). In some embodiments, the array of focused laser beams may include, for example, a plurality of focused laser beams (e.g., focused laser beams 834a-834d as discussed above with respect to FIG. 8D).

[0117] In some embodiments, each of the qudit components of flow diagrams 1500, 1600, 1700, 1800, 1900, and 2000 is a qubit that has two quantized states.III. Examples

[0118] The invention will be more fully understood by reference to the following examples. They should not, however, be construed as limiting the scope of the invention. It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.Example 1. Single Qudit Logical Operations

[0119] FIG. 21 illustrates a process for single qubit logic operations performed with a quantum information processing system in accordance with one or more embodiments. The quantum information processing system of FIG. 21 includes a quantum register comprising a plurality of qudit components, a qudit coherent control system coupled to the quantum register, and a controlled entropy source configured to couple to the qudit components of the quantum register. For the purposes of this example, the quantum register includes 6 qudits that are each a qubit with a ground state |0) and an excited state |1), however the methodology is applicable to scenarios employing higher dimensional qudit components. The qudit components may generally each be a single atom, a single ion, or a single photon.

[0120] In Frame 1 of FIG. 21, each of the qubit components is in the ground state, the coherent control system is not exerting a coherent control force, and none of the qubit components is coupled to the controlled entropy source. In Frame 2 of FIG. 21, the qudit coherent control system has begun exerting a coherent control force and all of the qubit components except for qubit #3 (QB 3 in FIG. 21) are subject to pumping of the excited state | 1) to a highly dissipative state, thereby coupling the qubits to the controlled entropy source. In this example, the coherent control force is a rotation force uniformly applied to all qubit components to simultaneously transition each of the qubit components to the excited state 11). However, each of the qubit components except for qubit #3 is coupled to the controlledentropy source, which applies continuous measurement to the qubit components to which it is coupled. Accordingly, with the strong, continuous measurement supplied by the controlled entropy source, qubits #1-2 and #4-6 (QB1, QB2, QB4, QB 5, and QB 6 of FIG. 21, respectively) are effectively frozen in the ground state with high probability due to the quantum Zeno effect. While the qubits coupled to the controlled entropy source are retained in the ground state with high probability in Frame 2 of FIG. 21, qubit #3 is not coupled to the controlled entropy source and begins to undergo transition from the ground state |0) to the excited state | 1). Accordingly, QB3 is depicted in superposition state a|0) + b| l) between the ground state and excited state in Frame 2 of FIG. 21.

[0121] Finally, Frame 3 of FIG. 21 depicts the result of the single qubit operation. In Frame 3, the rotation force has completed in transitioning qubit #3 from the ground state |0) to the excited state 11) while qubits #1-2 and #4-6 have all remained in the ground state with high probability due to the quantum Zeno effect from being coupled to the controlled entropy source effectuating strong measurement of the coupled qubits.Example 2. Conditional Logical Operations Between Qudits - Ground State Case

[0122] FIG. 22 illustrates a process for conditional logical operations between qubit components performed with a quantum information processing system in accordance with one or more embodiments. The quantum information processing system of FIG. 22 includes a quantum register comprising a plurality of qudit components, a qudit coherent control system coupled to the quantum register, and a controlled entropy source configured to couple to the qudit components of the quantum register. For the purposes of this example, the quantum register includes 6 qudits that are each a qubit with a ground state |0) and an excited state 11), however the methodology is applicable to scenarios employing higher dimensional qudit components. The qudit components may generally each be a single atom, a single ion, or a single photon.

[0123] In Frame 1 of FIG. 22, each of the qubit components is in the ground state, the coherent control system is not exerting a coherent control force, and none of the qubit components is coupled to the controlled entropy source. In Frame 2 of FIG. 22, the qudit coherent control system has begun exerting a coherent control force and all of the qubit components except for qubits #2-3 (QB2 and QB3 in FIG. 22, respectively) are subject to pumping of the excited state | 1) to a highly dissipative state, thereby coupling the qubits to the controlled entropy source. In this example, the coherent control force is a rotation forceuniformly applied to all qubit components to simultaneously transition each of the qubit components to the excited state | 1). However, each of the qubit components except for qubits #2-3 is coupled to the controlled entropy source, which applies continuous measurement to the qubit components to which it is coupled. Accordingly, with the strong, continuous measurement supplied by the controlled entropy source, qubits #1 and #4-6 (QB1, QB4, QB5, and QB6 of FIG. 22, respectively) are effectively frozen in the ground state with high probability due to the quantum Zeno effect. While the qubits coupled to the controlled entropy source are retained in the ground state with high probability in Frame 2 of FIG. 22, qubits #2-3 are subject to joint measurement, which will couple qubits #2-3 to a highly dissipative state only if either, but not both of qubits #2-3, are in the excited state 11). Consequently, for an arbitrary superposition state a|00) + b 101) + c| 10) + d 111) of qubits #2-3, the states 101) and 110) are removed, as depicted in Frame 2 of FIG. 22, leaving the states where qubits #2-3 are both in the ground state 100) or both in the excited state 111).

[0124] Finally, Frame 3 of FIG. 22 depicts the result of the operation. In Frame 3, qubits #2-3 have been entangled in a Bell statemeasurementand the remaining qubits #1 and #4-6 have each remained in the ground state |0) with high probability due to the quantum Zeno effect from being coupled to the controlled entropy source effectuating strong measurement of the coupled qubits.Example 3. Conditional Logical Operations Between Qudits - Arbitrary Case

[0125] FIG. 23 illustrates a process for conditional logical operations between qubit components performed with a quantum information processing system in accordance with one or more embodiments. The quantum information processing system of FIG. 23 includes a quantum register comprising a plurality of qudit components, a qudit coherent control system coupled to the quantum register, and a controlled entropy source configured to couple to the qudit components of the quantum register. For the purposes of this example, the quantum register includes 6 qudits that are each a qubit with a ground state |0) and an excited state 11), however the methodology is applicable to scenarios employing higher dimensional qudit components. The qudit components may generally each be a single atom, a single ion, or a single photon.

[0126] In Frame 1 of FIG. 23, qubit #3 (QB3 in FIG. 23) is initially in an arbitrary superposition state a|0) + b| l) and the each of the remaining qubit components is in the ground state. The coherent control system is not exerting a coherent control force, and noneof the qubit components is coupled to the controlled entropy source. In Frame 2 of FIG. 23, the qudit coherent control system has begun exerting a coherent control force and all of the qubit components except for qubits #2-3 (QB2 and QB3 in FIG. 23, respectively) are subject to pumping of the excited state 11) to a highly dissipative state, thereby coupling the qubits to the controlled entropy source. In this example, the coherent control force is a rotation force uniformly applied to all qubit components to simultaneously transition each of the qubit components to the excited state | 1). However, each of the qubit components except for qubits #2-3 is coupled to the controlled entropy source, which applies continuous measurement to the qubit components to which it is coupled. Accordingly, with the strong, continuous measurement supplied by the controlled entropy source, qubits #1 and #4-6 (QB1, QB4, QB5, and QB6 of FIG. 23, respectively) are effectively frozen in the ground state with high probability due to the quantum Zeno effect. While the qubits coupled to the controlled entropy source are retained in the ground state with high probability in Frame 2 of FIG. 23, qubits #2-3 are subject to joint measurement, which will couple qubits #2-3 to a highly dissipative state only if either, but not both of qubits #2-3, are in the excited state 11). Consequently, for an arbitrary superposition state10) + d' 111) of qubits #2-3, the states 101) and 110) are removed, as depicted in Frame 2 of FIG. 23, leaving the states where qubits #2-3 are in a coherent superposition of both qubits being in the ground state 100) or both qubits being in the excited state 111).

[0127] Finally, Frame 3 of FIG. 23 depicts the result of the operation. In Frame 3, qubits #2-3 have been entangled in a state a" 100) + b"\ 11) due to the joint measurement, where the final values of a" and b" depend on the initial arbitrary superposition state a|0) + b| l) of qubit #3 in Frame 1 of FIG. 23. The remaining qubits #1 and #4-6 have each remained in the ground state |0) with high probability due to the quantum Zeno effect from being coupled to the controlled entropy source effectuating strong measurement of the coupled qubits.

Claims

CLAIMS1. A quantum information processing system comprising: a quantum register comprising an array of qudit components, wherein each qudit component comprises at least two quantized states; a qudit coherent control system coupled to the quantum register and configured to exert a coherent state transformation to the qudit components of the quantum register; and a controlled entropy source configured to couple to the qudit components of the quantum register to apply continuous or periodic measurement to the qudit components that are coupled to the controlled entropy source.

2. The quantum information processing system of claim 1, wherein the qudit coherent control system comprises at least one pumping laser that coherently changes or amplifies the states of the qudit components of the quantum register.

3. The quantum information processing system of claim 1 or 2, wherein the controlled entropy source comprises an array of focused laser beams or electro-optical modulation devices.

4. The quantum information processing system of any one of claims 1-3, wherein each of the qudit components of the quantum register is a single atom, a single ion, or a single photon.

5. The quantum information processing system of any one of claims 1-4, wherein the coherent state transformation is a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the controlled entropy source applies continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state.

6. The quantum information processing system of claim 1, further comprising: a quantum measurement port coupled to the qudit components of the quantum register and configured to receive measurement results from the qudit components of the quantum register; anda feedback control unit, wherein the feedback control unit couples the quantum measurement port and the controlled entropy source and is configured to generate controlling sequences from the measurement results received by the quantum measurement port to control the entropy source and / or to modulate the coupling of the qudit components to the entropy source.

7. The quantum information processing system of claim 6, wherein the qudit coherent control system comprises at least one pumping laser that coherently changes or amplifies the states of the qudit components of the quantum register.

8. The quantum information processing system of claim 6 or 7, wherein the controlled entropy source comprises an array of focused laser beams or electro-optical modulation devices.

9. The quantum information processing system of any one of claims 6-8, wherein each of the qudit components of the quantum register is a single atom, a single ion, or a single photon.

10. The quantum information processing system of any one of claims 6-9, wherein the coherent state transformation is a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the controlled entropy source applies continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state.

11. The quantum information processing system of any one of claims 1-10, wherein each of the qudit components is a qubit that has two quantized states.

12. A quantum information processing system comprising: a quantum register comprising an array of qudit components, wherein each qudit component comprises at least two quantized states; a qudit coherent control system coupled to the quantum register and configured to exert a coherent state transformation to the qudit components of the quantum register; a quantum feedback channel coupled to the quantum register, the quantum feedback channel configured to induce controlled loss of information to the qudit components of thequantum register according to the quantum states of the qudit components of the quantum register.

13. The quantum information processing system of claim 12, wherein the qudit coherent control system comprises at least one pumping laser that coherently changes or amplifies states of the qudit components of the quantum register.

14. The quantum information processing system of claim 12 or 13, wherein each of the qudit components of the quantum register is a single atom, a single ion, or a single photon.

15. The quantum information processing system of any one of claims 12-14, wherein the quantum feedback channel comprises an array of focused laser beams or electro-optical modulation devices.

16. The quantum information processing system of any one of claims 12-15, wherein each of the qudit components is a qubit that has two quantized states.

17. A method for operating a quantum information processing system, comprising: applying a coherent control force to qudit components of a quantum register of the quantum information processing system to dynamically evolve the qudit components; and coupling at least one of the qudit components of the quantum register to a controlled entropy source of the quantum information processing system to apply measurement pulses to the subset of qudit components coupled to the controlled entropy source to alter the coherent dynamics of the qudit components through backactions induced by quantum measurements.

18. The method of claim 17, wherein the qudit components are all each initially in a ground state.

19. The method of claim 17 or 18, wherein at least one select qudit component is not coupled to the controlled entropy source, and the method further comprises:maintaining the coherent control force and the coupling between the at least one qudit component and the controlled entropy source until the at least one select qudit component is in a desirable state.

20. The method of any one of claims 17-19, wherein the coherent control force is a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the controlled entropy source applies continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state.

21. The method of claim 17 or 18, wherein at least two select qudit components are not coupled to the controlled entropy source, and the method further comprises: maintaining the coherent control force and the coupling between the at least one qudit component and the controlled entropy source while entangling the at least two select qudit components by subjecting the at least two select qudit components to joint measurement.

22. The method of claim 21, wherein the coherent control force is a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the controlled entropy source applies continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state.

23. The method of claim 17, wherein a first select qudit component is initially in an arbitrary superposition state and the remainder of the qudit components are initially in the ground state.

24. The method of claim 17 or 23, wherein the subset of qudit components does not include the first select qudit component and at least one additional select qudit component of the quantum register, and the method further comprises: maintaining the coherent control force and the coupling between the at least one qudit component and the controlled entropy source while entangling the first and at least one additional select qudit components by subjecting the first and at least one additional select qudit components to joint measurement.

25. The method of claim 23 or 24, wherein the coherent control force is a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the controlled entropy source applies continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state.

26. The method of any one of claims 17-25, wherein each of the qudit components is a qubit that has two quantized states.

27. A method for operating a quantum information processing system, comprising: applying a coherent control force to qudit components of a quantum register of the quantum information processing system to dynamically evolve the qudit components; and coupling at least one of the qudit components of the quantum register to a quantum feedback channel of the quantum information processing system to induce controlled loss of information to the qudit components of the quantum register according to the quantum states of the qudit components of the quantum register.

28. The method of claim 27, wherein the qudit components are all each initially in a ground state.

29. The method of claim 27 or 28, wherein at least one select qudit component is not coupled to the quantum feedback channel, and the method further comprises: maintaining the coherent control force and the coupling between the at least one qudit component and the quantum feedback channel until the at least one select qudit component is in a desirable state.

30. The method of any one of claims 27-29, wherein the coherent control force is a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the quantum feedback channel appliescontinuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state.

31. The method of claim 27 or 28, wherein at least two select qudit components are not coupled to the quantum feedback channel, and the method further comprises: maintaining the coherent control force and the coupling between the at least one qudit component and the quantum feedback channel while entangling the at least two select qudit components by subjecting the at least two select qudit components to joint measurement.

32. The method of claim 31, wherein the coherent control force is a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the quantum feedback channel applies continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state.

33. The method of claim 27, wherein a first select qudit component is initially in an arbitrary superposition state and the remainder of the qudit components are initially in the ground state.

34. The method of claim 27 or 33, wherein the subset of qudit components does not include the first select qudit component and at least one additional select qudit component of the quantum register, and the method further comprises: maintaining the coherent control force and the coupling between the at least one qudit component and the quantum feedback channel while entangling the first and at least one additional select qudit components by subjecting the first and at least one additional select qudit components to joint measurement.

35. The method of claim 33 or 34, wherein the coherent control force is a rotation force uniformly applied to the qudit components to simultaneously transition each of the qudit components to an excited state and the quantum feedback channel applies continuous measurement to the qudit components at a greater rate than the rotation force can transition the qudit components to the excited state.

36. The method of any one of claims 27-35, wherein each of the qudit components is a qubit that has two quantized states.

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