Devices for quantum computing

Abstract

According to one embodiment, an apparatus for quantum computing comprises a plurality of quantum computing units, each quantum computing unit comprising a plurality of qubits arranged to perform a quantum computation according to a plurality of control signals and to provide at least one output signal according to a result of the quantum computation; a control unit for providing the plurality of control signals; a signal distribution device for transmitting the plurality of control signals to the plurality of quantum computing units, the signal distribution device configured to distribute each control signal to each quantum computing unit, the control unit configured to cause each quantum computing unit to perform a separate instance of a quantum computation; and a readout unit configured to obtain at least one output signal from each quantum computing unit and to perform at least one statistical operation based on the output signals, thereby obtaining an overall quantum computing result.

Description

Technical Field

[0001] The present disclosure relates to quantum computing, and more particularly, to an apparatus for quantum computing and a quantum computing system.

Background Art

[0002] Quantum computing has been predicted to achieve an exponential speedup compared to classical computing in certain tasks. However, the results from quantum computing can be nondeterministic due to non-ideality in the quantum computing unit or from the principles of certain methodologies used in quantum computing. Therefore, quantum computations typically need to be run multiple times to obtain meaningful results. This significantly increases the total execution time of quantum computing, which can thus impede the overall performance of quantum computing and limit its scope of application. While a single quantum processor can have a large number of qubits, typically only one or at most a few are set up due to issues in wiring, calibration, and fabrication complexity of high-quality quantum processor copies, thus limiting the number of internal quantum processors.

Summary of the Invention

Means for Solving the Problems

[0003] This summary is provided to introduce, in a simplified form, a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0004] >An object is to provide an apparatus for quantum computing and a quantum computing system. The foregoing and other objects are achieved by the features of the independent claims. Further implementations are apparent from the dependent claims, the description, and the figures.

[0005] According to a first embodiment, the apparatus for quantum computing comprises: a plurality of quantum computing units, each having a plurality of qubits arranged to perform quantum computation according to a plurality of control signals provided to the quantum computing unit and to provide at least one output signal according to the result of the quantum computation; a control unit for providing the plurality of control signals to the plurality of quantum computing units; a signal distribution device for transmitting the plurality of control signals generated from the control unit to the plurality of quantum computing units, wherein the signal distribution device is configured to distribute each of the plurality of control signals generated from the control unit to each quantum computing unit in the plurality of quantum computing units, and the control unit is configured to cause each quantum computing unit in the plurality of quantum computing units to perform a separate instance of quantum computation via the plurality of control signals and the signal distribution device; and a readout unit configured to obtain at least one output signal from each quantum computing unit in the plurality of quantum computing units, perform at least one statistical operation based on the output signal, and thereby obtain an overall quantum computation result. The apparatus can, for example, obtain results for quantum computation at a faster speed.

[0006] In one implementation of the first embodiment, each quantum computing unit in a plurality of quantum computing units corresponds to a quantum processing unit (QPU), a core in a multicore QPU, or a subunit of a QPU. This device can be implemented, for example, with various levels of integration.

[0007] In another implementation of the first embodiment, the signal distribution device is configured to distribute each control signal in a plurality of control signals generated from a control unit to each quantum computing unit in a plurality of quantum computing units using at least one T-junction, at least one power divider, at least one Wilkinson power divider, at least one directional coupler and / or at least one hybrid coupler. The device can efficiently distribute, for example, radio frequency control signals to a plurality of quantum computing units.

[0008] In another implementation of the first embodiment, the apparatus further comprises a tuning device configured to adjust at least one characteristic of a plurality of control signals distributed by a signal distribution device, wherein the at least one characteristic includes at least one of frequency, amplitude, phase and / or relative timing. The apparatus can fine-tune the control signals according to the characteristics of each quantum computing unit, for example.

[0009] In another implementation of the first embodiment, the tuning device further comprises at least one voltage-controlled attenuator configured to adjust at least one control signal in a plurality of control signals distributed by a signal distribution device. This device can efficiently fine-tune, for example, a radio frequency control signal.

[0010] In another implementation of the first embodiment, at least one voltage-controlled attenuator comprises at least one high-electron-mobility transistor, at least one tuneable reactive impedance element, at least one superconducting quantum interference device and / or at least one varactor diode. This device can, for example, efficiently fine-tune a radio frequency control signal.

[0011] In another implementation of the first embodiment, output signals from multiple quantum computing units are time-multiplexed, and the readout unit is further configured to obtain output signals from each of the multiple quantum computing units according to the time-multiplexing. The device can transmit output signals from the quantum computing units to the readout unit using, for example, a reduced number of signal lines.

[0012] In another implementation of the first embodiment, the apparatus further comprises a delay line configured to be coupled to a plurality of quantum computing units and to time-multiplex the output signals from the plurality of quantum computing units. The apparatus can, for example, efficiently time-multiplex the output signals via the delay line.

[0013] In another implementation of the first embodiment, the read unit further comprises an adder, and the read unit is configured to perform at least one statistical operation based on the output signal by coherently adding the output signal via the adder. This device can efficiently perform at least one statistical operation, for example, via coherent addition.

[0014] In another implementation of the first embodiment, each quantum computing unit in a plurality of quantum computing units further comprises a plurality of frequency tuning elements configured to tune the qubit frequencies of a plurality of qubits according to a frequency tuning signal. This device can, for example, fine-tune the qubit frequencies.

[0015] In another implementation of the first embodiment, each quantum computing unit in a plurality of quantum computing units further comprises a plurality of capacitance tuning elements configured to tune the capacitances of a plurality of qubits according to a capacitance tuning signal. This device can, for example, fine-tune the qubit capacitances.

[0016] In another implementation of the first embodiment, the qubits comprise superconducting qubits.

[0017] In another implementation form of the first aspect, at least one statistical operation includes at least one of mean, variance and / or cross-entropy.

[0018] In another implementation form of the first aspect, the apparatus further includes a cryostat, and the plurality of quantum computing units and the signal distribution device are arranged inside the cryostat. The apparatus can, for example, reduce the number of signal lines that need to be extended into the cryostat.

[0019] According to the second aspect, a quantum computing system includes a plurality of apparatuses according to the first aspect.

[0020] Many of the accompanying features will be more readily understood as they are better understood by reference to the following detailed description considered in conjunction with the accompanying drawings.

[0021] Embodiment examples are described in more detail below with reference to the accompanying figures and drawings.

Brief Description of the Drawings

[0022] [Figure 1] It is a schematic diagram of an apparatus for quantum computing according to an embodiment. [Figure 2] It is a schematic diagram of an apparatus for quantum computing further including a synchronization device according to an embodiment. [Figure 3] It is a schematic diagram of an apparatus for quantum computing further including a delay line according to an embodiment. [Figure 4] It is a schematic diagram of a qubit and a frequency synchronization element according to an embodiment. [Figure 5] It is a schematic diagram of a control unit according to an embodiment.

Modes for Carrying Out the Invention

[0023] In the following, like reference numerals are used to denote like parts in the accompanying drawings.

[0024] In the following description, the accompanying drawings, which are referred to, form a part of this disclosure and illustrate, by way of example, specific embodiments in which the disclosure may be set. It is understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the disclosure. The following detailed description is, therefore, not to be taken in a limiting sense, nor is it the scope of the appended patent claims that defines the scope of the disclosure.

[0025] It is understood, for example, that the disclosure related to a described method also applies to a corresponding device or system configured to perform that method, and vice versa. For example, when steps of a particular method are described, a corresponding device may include such units even if units performing the steps of the described method are not explicitly described or illustrated in the figures. On the other hand, for example, when a particular device is described based on functional units, a corresponding method may include such steps even if steps performing the described functions are not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary embodiments described herein may be combined with each other unless otherwise specifically noted.

[0026] FIG. 1 illustrates a schematic diagram of a device for quantum computing according to one embodiment.

[0027] According to one embodiment, the device 100 includes a plurality of quantum computing units 101, and each quantum computing unit includes a plurality of qubits arranged to perform quantum computing according to a plurality of control signals provided to the quantum computing unit and to provide at least one output signal according to the result of the quantum computing.

[0028] The multiple qubits may consist of superconducting qubits, such as transmon qubits, flux qubits, charge qubits, phase qubits, or flaxonium qubits.

[0029] Some embodiments may be disclosed herein with reference to certain types of qubits, the types of qubits being described herefore as illustrative. In any embodiment disclosed herein, multiple qubits may be implemented in various forms and using various techniques.

[0030] Each control signal in a set of multiple control signals can control, for example, the coupling between qubits, the initialization of qubits, the state of qubits, and / or any other properties of qubits required to perform quantum computation.

[0031] The control signal may consist of, for example, a radio frequency (RF) signal or an optical signal, depending on the implementation of the multiple quantum computing units 101.

[0032] The output signal may also be referred to as the readout signal, etc.

[0033] Control signals may also be referred to as control voltages, control pulses, etc.

[0034] The device 100 may further include a control unit 102 for providing a plurality of control signals 104 to a plurality of quantum computing units 101.

[0035] Although the embodiment in Figure 1 illustrates only one signal line originating from the control unit 102, this is simply for illustrative purposes. There may be any number of signal lines originating from the control unit 102. For example, if N control signals are required for each quantum computing unit in a plurality of quantum computing units 101, then a plurality of control signals 104 may consist of N control signals, and for each control signal, there may be a corresponding signal line originating from the control unit 102.

[0036] The device 100 may further include a signal distribution device 103 for transmitting a plurality of control signals 104 generated from a control unit 102 to a plurality of quantum computing units 101. The signal distribution device 103 may be configured to distribute each of the control signals 104 generated from the control unit 102 to each quantum computing unit in the plurality of quantum computing units 101.

[0037] For example, if N control signals are required for each quantum computing unit, the multiple control signals 104 may contain N control signals. The signal distributor 103 can distribute each of the N control signals to each quantum computing unit in the multiple quantum computing units 101 so that N control signals are provided to each quantum computing unit. Therefore, if there are M quantum computing units in the multiple quantum computing units 101, the signal distributor 103 may be configured to output N × M control signals.

[0038] The signal distribution device 103 may also be called a fan-out device, signal distribution device, distributor, one-to-many device, etc.

[0039] The control unit 102 may be configured to cause each quantum computing unit in the plurality of quantum computing units 101 to execute a separate instance of quantum computation via a plurality of control signals 104 and a signal distribution device 103.

[0040] Each quantum computing unit in the multiple quantum computing units 101 may be nominally identical. Therefore, each quantum computing unit may perform quantum computations in the same manner.

[0041] Since the signal distribution device 103 can distribute each control signal in the multiple control signals 104 to each quantum computing unit in the multiple quantum computing units 101, each quantum computing unit can execute a separate instance of quantum computation. However, the results of quantum computation may be nondeterministic, for example, due to non-idealism in the quantum computing unit or due to the principles of a certain quantum computing method, and therefore each quantum computing unit may not produce the same result in quantum computation.

[0042] An instance of quantum computing may refer to a separate execution of quantum computing. Each instance can perform quantum computing independently of other instances. Due to the non-deterministic nature of quantum computing, each instance of quantum computing may not produce the same result.

[0043] Each quantum computing unit in the multiple quantum computing units 101 can be a separate unit in the sense that there is no quantum coherence shared across the multiple quantum computing units 101. Therefore, each quantum computing unit can perform quantum computations independently of the others.

[0044] Quantum computing can also be referred to as quantum algorithms, quantum circuits, etc.

[0045] The device 100 may further include a readout unit 105 configured to obtain at least one output signal 106 from each of the multiple quantum computing units 101, perform at least one statistical operation based on the output signals 106, and thereby obtain an overall quantum computation result.

[0046] Since the results of quantum computation may be non-deterministic in each of the multiple quantum computing units 101, the readout unit 105 may need to perform statistical operations on the results to obtain an overall quantum computation result.

[0047] The overall quantum computation result may refer to the computation result obtained based on the results of each instance of the quantum computation. For example, the overall quantum computation result may correspond to the average across the results of different instances.

[0048] According to one embodiment, at least one statistical operation includes at least one of the mean, variance, and / or cross-entropy.

[0049] According to one embodiment, the signal distribution device 103 is configured to distribute each control signal in a plurality of control signals 104 generated from the control unit 102 to each quantum computing unit in a plurality of quantum computing units 101 using at least one T-junction, at least one power distributor, at least one Wilkinson power distributor, at least one directional coupler and / or at least one hybrid coupler.

[0050] The components for distributing each control signal in the plurality of control signals 104 disclosed above are merely illustrative. Alternatively, the signal distributor 103 may be configured to distribute each control signal in the plurality of control signals 104 originating from the control unit 102 to each quantum computing unit in the plurality of quantum computing units 101 using one or more signal distributors of any other type.

[0051] The device 100 can accelerate quantum computation by, for example, operating multiple quantum computing units 101 substantially simultaneously, rather than repeating the same quantum computation many times on a single quantum computing unit. The device 100 can, for example, operate many similar (ideally identical) quantum computing units across the entire quantum computing unit network rather than over time to collect statistics. For example, to achieve an accuracy of 1e-3, one million samples are required. Instead of running the same quantum computation on one quantum computing unit for 17 minutes, the same averaging can be done in a one-shot of one millisecond on one million quantum computing units. This can be beneficial, for example, for variational quantum algorithms, where the computation may need to be repeated thousands or more times with different parameters. The device 100 can enable feasible execution times for such algorithms, for example, by considering the integration of high-performance computing, as well as the exchange of data between classical and quantum computing steps. Another example is high-frequency trading in financial applications, where fractions of a second of clock time may be available for decision-making. Quantum computing algorithms could be powerful for analyzing financial data, but previously they were unsuitable for this purpose because the iteration of the algorithms took too much time.

[0052] Multiple quantum computing units 101 can be placed in one or more dilution refrigerators. Similar control signals can be supplied to the multiple quantum computing units 101, and their outputs can be read separately by the readout unit 105 and post-processed, such as averaging.

[0053] In some embodiments, the signal distribution device 103 may be placed in one or more dilution refrigerators. Dilution refrigerators may also be referred to as cryostats.

[0054] To overcome the numerous control signal lines required to operate multiple quantum computing units, the device 100 includes a fan-out device 103 through which multiple control signals 104 can be distributed to each quantum computing unit in the multiple quantum computing units 101.

[0055] The control signal 104 can be a high frequency signal such as multiple gigahertz or terahertz, an RF signal, or an electromagnetic signal such as an optical signal. Generating such a signal can be a technically complex task. The signal distribution device 103 can reduce the need for multiple high-frequency signal sources, signal lines, and / or other electronic components, thereby reducing the technical complexity of the device 100.

[0056] The signal distribution device 103 may include a distributor capable of distributing a single input signal to multiple paths addressing qubits in different quantum computing units in multiple quantum computing units 101. Signal distribution can be performed in various forms. Different implementations may have different signal integrity, cross-coupling properties, losses, physical size, and accessible frequency bands.

[0057] For example, a distributor can consist of a T-piece that performs a 1:2 distribution of an RF signal, or a more general-purpose distributor that performs a 1:N distribution. The ports of the distributor can be unmatched. A further generalization of the 1:2 distributor is the Wilkinson power distributor, which has a microwave loss mechanism and is matched at all ports. Distribution can also be done with directional couplers such as 3dB hybrids. In addition to cascading many distributor stages to generate more output, generalizations and / or combinations of the above examples are also practical.

[0058] The signal distribution device 103 may further include impedance matching circuits, filters, isolators, attenuators, or any other signal conditioning elements to improve matching, noise reduction, and / or isolation of different ports.

[0059] In embodiments where multiple quantum computing units 101 are based on neutral atom qubits, such as nitrogen-vacancy (NV) center qubits, ion trap qubits, and / or Rydberg atoms, the control signal 104 may consist of coherent light from a laser, and the signal distribution device 103 may comprise, for example, one or more beam splitters. The laser may be in different wavelength ranges for the techniques described above.

[0060] According to one embodiment, each quantum computing unit in the plurality of quantum computing units 101 corresponds to a quantum processing unit (QPU), a core in a multi-core QPU, or a subunit of a QPU.

[0061] According to one embodiment, the apparatus 100 further comprises a cryostat, and a plurality of quantum computing units 101 and a signal distribution device 103 are arranged inside the cryostat. Therefore, since the signal distribution device 103 can distribute signals inside the cryostat, the number of signal lines that need to be extended into the cryostat can be reduced. The control unit 102 can be arranged outside the cryostat.

[0062] The features disclosed herein can be implemented at various different levels of integration. For example, different QPU cores may reside on the same chip, or the QPU cores may reside on different chips in a single package. The package may be based on connecting the chips by wire bonding, or there may be a flip-chip solution in which one or more carrier chips connect to one or more QPU cores. The carrier chips may include all or some of the microwave engineering solutions disclosed herein. Instead of carrier chips, a printed circuit board (PCB) may comprise the chips.

[0063] Figure 2 illustrates a schematic diagram of a quantum computing apparatus 100 further comprising a tuning device 201 according to one embodiment.

[0064] For example, manufacturing-related differences in multiple quantum computing units 101 may necessitate fine-tuning of the control signals after the signal distribution device 103.

[0065] According to one embodiment, the apparatus 100 further comprises a tuning device 201 configured to adjust the characteristics of at least one of a plurality of control signals distributed by a signal distribution device 103. The at least one characteristic may include at least one of frequency, amplitude, phase and / or relative timing.

[0066] For example, in the embodiment shown in Figure 2, the tuning device 201 comprises a tuning unit 202 and a plurality of tuning elements 203 coupled to the tuning unit 202. In the embodiment shown in Figure 2, only a single tuning element 203 is depicted for each quantum computing unit. However, there may be separate tuning elements 203 for each control signal output by the signal distribution device 103, for example.

[0067] In some embodiments, the tuning unit 202 and the control unit 102 may be implemented by a single device. In some other embodiments, there may be a tuning unit 202 for each quantum computing unit in a plurality of quantum computing units 101.

[0068] According to one embodiment, the tuning device 201 further comprises at least one voltage-controlled attenuator configured to adjust at least one control signal in a plurality of control signals distributed by the signal distribution device 103.

[0069] According to one embodiment, at least one voltage-controlled attenuator comprises at least one high-electron-mobility transistor, at least one tuneable reactive impedance element, at least one superconducting quantum interference device and / or at least one varactor diode.

[0070] The tuning device 201 may include, for example, a voltage-controlled attenuator capable of adjusting the amplitude of the control signal. The voltage-controlled attenuator may be implemented, for example, via a high-electron-mobility transistor (HEMT) used as a voltage-controlled resistor, which is preferably supplemented by a passive resistor. Alternatively, the attenuator may comprise a tunable reactive impedance element implemented via a superconducting quantum interference device (SQUID) or a SQUID array or circuit based on a varactor diode. In some embodiments, precise phase control may be required, and therefore a phase shifter based on the reactance element described above may also be used.

[0071] In some embodiments, the device 100 may further include a second tuning device for the output signal 106. Any disclosure herein relating to the tuning device 201 may also apply to the second tuning device.

[0072] Figure 3 illustrates a schematic diagram of a quantum computing apparatus 100 further comprising a delay line 301 according to one embodiment.

[0073] According to one embodiment, the output signals 106 from the multiple quantum computing units 101 are time-multiplexed, and the readout unit 105 is further configured to obtain output signals from each quantum computing unit in the multiple quantum computing units 101 according to the time-multiplexing.

[0074] According to one embodiment, the apparatus 100 further comprises a delay line 301 coupled to a plurality of quantum computing units 101 and configured to time-multiplex output signals 106 from the plurality of quantum computing units.

[0075] Qubit readout can be arranged, for example, by time-multiplexing the output signal / pulse using delay lines, i.e., by separating them in time. The physical length of each delay line can be controlled using, for example, a high-inductance metamaterial or a conversion to sound waves, such as one based on a Josephson junction. The delay line 301 can also be made tunable, for example, by using a flux-controlled Josephson metamaterial.

[0076] Figure 4 illustrates a schematic diagram of a qubit and frequency tuning element according to one embodiment.

[0077] Small fabrication differences between qubits and other quantum computing unit elements in multiple quantum computing units 101, as well as changing environmental conditions, may require in-situ tuning.

[0078] According to one embodiment, each quantum computing unit in the plurality of quantum computing units 101 further comprises a plurality of frequency tuning elements configured to tune the qubit frequencies of a plurality of qubits according to a frequency tuning signal.

[0079] For example, each qubit in a group of qubits may be coupled to a corresponding frequency-tuning element. For superconducting qubits implemented using superconducting quantum interference devices (SQUIDs), this can be done by controlling the magnetic flux with a DC or radio frequency signal to control the Josephson coupling energy, and therefore the qubit frequency.

[0080] Each qubit may have a ground state |g〉. In this specification, the ground state may refer to the quantum state of the qubit with the lowest energy.

[0081] Each qubit may further have at least one excited state, the at least one excited state may include the lowest excited state |e〉. In this specification, the lowest excited state may refer to the quantum state of the qubit with the second lowest energy.

[0082] The ground state and lowest excited state of a qubit may correspond to the computational basis of the qubit. For example, the ground state |g〉 may correspond to the |0〉 state of the qubit, the lowest excited state |e〉 may correspond to the |1〉 state of the qubit, and vice versa. Other quantum states of the qubit may be called non-computational states.

[0083] The energy gap between the ground state and the lowest excited state may correspond to the qubit's resonant frequency. The energy gap may also be called the qubit energy, and the corresponding frequency may be called the qubit frequency.

[0084] In the embodiment shown in Figure 4, the qubit 405 comprises a SQUID 401 and a capacitive circuit 404. A corresponding frequency tuning element 402 is provided for the SQUID 401. The frequency tuning element 402 is electrically coupled to a signal line 403. A frequency tuning signal can be provided via the signal line 403. By supplying a frequency tuning signal to the signal line 403, the qubit frequency of the qubit 405 can be adjusted. This may be referred to as magnetic flux tuning, where the magnetic flux generated by the frequency tuning element 402 shifts the corresponding qubit frequency of the qubit 405.

[0085] In other embodiments, two or more qubits can be implemented by combining the SQUID 401 and the capacitive circuit 404, similar to the embodiment in Figure 4. For each qubit 405, there may be a corresponding frequency tuning element 402, for example, consisting of a resonator. The resonator can be electrically coupled to a signal line 403. A frequency tuning signal can be provided via the signal line 403. The qubit frequency of the corresponding qubit 405 can be adjusted by supplying a signal having a frequency corresponding to the resonant frequency of the resonator. Since each resonator may have a different resonant frequency, each resonator can be addressed using the same signal line 403 by appropriately selecting the frequency of the addressing signal.

[0086] The embodiments disclosed herein are merely examples of qubit frequency tuning, and frequency tuning can be implemented in various other ways. For example, each qubit may comprise a SQUID tuning loop, and the frequency tuning signal consists of a direct current (DC) signal configured to change the DC magnetic flux passing through the SQUID tuning loop.

[0087] According to one embodiment, each quantum computing unit in the plurality of quantum computing units 101 further comprises a plurality of capacitance tuning elements configured to tune the capacitances of a plurality of qubits according to a capacitance tuning signal.

[0088] For example, each qubit in a plurality of qubits may be coupled to a corresponding capacitive tuning element. Each capacitive tuning element may be configured to tune the capacitance of the corresponding qubit in response to a corresponding capacitive tuning signal. The capacitive tuning signal can be provided, for example, by the control unit 102 or by any other device / unit / module.

[0089] Capacitive tuning elements can compensate for small fluctuations in the qubit's charge energy, which can affect fidelity by causing entanglement in the 2-qubit gate operation, as these fluctuations affect the spectrum of the qubit's non-calculated state. Each capacitive tuning element can consist of, for example, a metal plate attached to a piezoelectric actuator.

[0090] For example, a transmon qubit may comprise two metallic (superconducting) electrodes connected to a Josephson junction. The qubit capacitance is the capacitance between the two electrodes, determined by the geometric arrangement of the electrodes and nearby dielectrics. If the geometry is deformed, the qubit capacitance will change. Geometric deformation can be implemented, for example, using a third movable metallic electrode. The third metallic electrode can be moved, for example, using a piezoelectric element controlled by a capacitance tuning signal.

[0091] According to one embodiment, the reading unit 105 further comprises an adder, and the reading unit 105 is configured to perform at least one statistical operation based on the output signal 106 by coherently adding the output signal 106 via the adder.

[0092] For example, an adder may comprise at least one adder element. The output signals 106 can be added using at least one adder element. The implementation of at least one adder element may depend on the implementation of multiple quantum computing units 101. For example, if multiple quantum computing units 101 comprise superconducting qubits, the output signals 106 may consist of RF signals. In such a case, at least one adder element may consist of, for example, one or more RF combiners. If multiple quantum computing units 101 comprise NV qubits, ion trap qubits, or neutral atom qubits, the output signals 106 are optical signals. In such a case, at least one adder element may consist of one or more optical couplers, optical combiners, or any other component capable of adding optical signals.

[0093] In some embodiments, the output signals are coherently added before amplification. The advantage of this may be that only one amplifier chain is required after the addition. Alternatively, the output signals may be coherently added after amplification. Adding the output signals can be equivalent to taking the average of the output signals.

[0094] Each quantum computing unit in the multiple quantum computing units 101 may have one or more output lines. Each output line may provide a corresponding output signal. Each output line may enable reading the state of each qubit in a subset of qubits using frequency multiplexing.

[0095] Each output line may include a readout chain. The readout chain may include, for example, an amplification chain, a digital signal processor (DSP), and a discriminator that assigns a binary result ("0" or "1") to each qubit measurement.

[0096] If the statistical calculation is the average of each individual qubit read, the statistical calculation can be performed at any point in the read chain or by counting the proportion of "1" measurement results.

[0097] In embodiments requiring only the overall average single qubit readout result, the output signals 106 from each quantum computing unit can be coherently added before the amplification chain. This can be implemented, for example, by coupling the readout resonators of all quantum computing units to the same microwave feed line and correcting amplitude and phase misalignments between quantum computing units with the aforementioned tunable elements.

[0098] Alternatively, the expectation value of an arbitrary function of the measured bit string can be evaluated. The measured bit string can include binary results for each qubit in a quantum computing unit. In this case, a separate read chain may be required for each read line in each quantum computing unit. Each execution instance of quantum computation becomes a new bit string. The set of bit strings can be used as the output of a sampling problem. From a sample of bit strings, for example, cross-entropy can be calculated. Cross-entropy can be used, for example, in cross-entropy benchmarking (XEB), where each bit string observed experimentally can often be compared to its corresponding ideal probability calculated through simulation on a classical computer.

[0099] In some embodiments, the readout unit 105 can apply error correction to the output signal before performing at least one statistical operation. The error correction can be applied at this stage based on the measurement results without requiring quantum operations that depend on the measurement results.

[0100] Figure 5 illustrates a schematic diagram of a control unit 102 according to one embodiment.

[0101] The control unit 102 may include at least one processor 601. The at least one processor 601 may consist of one or more of various processing devices, such as a coprocessor, microprocessor, digital signal processor (DSP), processing circuit with or without an associated DSP, or various other processing devices, such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), microprocessor units (MCUs), hardware accelerators, dedicated computer chips, etc.

[0102] The control unit 102 may further include a memory 602. The memory 602 may be configured to store, for example, computer programs. The memory 602 may consist of one or more volatile memory devices, one or more non-volatile memory devices, and / or a combination of one or more volatile memory devices and non-volatile memory devices. For example, the memory 602 may be embodied as a magnetic storage device (such as a hard disk drive or magnetic tape), a magneto-optical storage device, and a semiconductor memory (such as a mask ROM, PROM (programmable ROM), EPROM (erasable PROM), flash ROM, RAM (random access memory), etc.).

[0103] The control unit 102 may further include other components not illustrated in the embodiment of Figure 6. The control unit 102 may include, for example, an input / output bus for connecting the control unit 102 to other devices. Furthermore, a user may control the control unit 102 via the input / output bus. The user may, for example, control quantum computation operations performed by the device 100 via the control unit 102 and the input / output bus.

[0104] The control unit 102 may further include appropriate signal sources for generating and controlling the control signal 104. For example, the control unit 102 may include at least one RF signal source and / or at least one optical signal source, such as at least one laser.

[0105] When the control unit 102 is configured to implement a certain function, one or more components of the control unit 102, such as at least one processor 601 and / or memory 602, may be configured to implement this function. Furthermore, when at least one processor 601 is configured to implement a certain function, this function may be implemented, for example, using program code stored in memory.

[0106] The control unit 102 may be implemented, at least partially, using, for example, a computer, or some other computing device.

[0107] Any range or device value given herein may be extended or modified without loss of the desired effect. Furthermore, any embodiment may be combined with another embodiment unless expressly denied.

[0108] While the subject matter is described in terms specific to structural features and / or actions, it should be understood that the subject matter defined in the attached claims is not necessarily limited to the specific features or actions described above. Rather, the specific features and actions described above are disclosed as examples of implementing the claims, and other equivalent features and actions are intended to be within the scope of the claims.

[0109] It will be understood that the above-mentioned benefits and advantages may apply to one embodiment or to several embodiments. Embodiments are not limited to those that solve any or all of the specified problems or that have any or all of the specified benefits and advantages. It will further be understood that a reference to "one" item may refer to one or more of those items.

[0110] The steps of the methods described herein may be performed in any suitable order, or simultaneously as necessary. Additionally, any individual block may be removed from the method without departing from the spirit and scope of the subject matter described herein. Any aspect of the embodiments described above may be combined with any aspect of any of the other embodiments described without losing the desired effect to form further embodiments.

[0111] The term “equipped with” is used herein to mean that a method, block, or element is included, but such block or element does not constitute an exclusive list, and the method or apparatus may include additional blocks or elements.

[0112] It will be understood that the above description is given merely as an example and that various modifications can be made by those skilled in the art. The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments. Although various embodiments have been described above in some detail or by reference to one or more individual embodiments, those skilled in the art can make numerous modifications to the embodiments disclosed without departing from the spirit or scope of this specification. [Explanation of Symbols]

[0113] 100 Devices for Quantum Computing 101 Quantum Computing Unit 102 Control Unit 103 Signal distribution device 104 Control signal 105 Reading Unit 106 Output signal 201 Tuning device 202 Synchronization Unit 203 Tuning element 301 Delay Line 401 Superconducting Quantum Interference Devices (SQUIDs) 402 Frequency tuning element 403 signal line 404 Capacitive circuit 405 Cubits 601 Processor 602 memory

Claims

1. A device (100) for quantum computing, A plurality of quantum computing units (101), each comprising a plurality of qubits arranged to perform quantum computation according to a plurality of control signals provided to the quantum computing unit and to provide at least one output signal according to the result of the quantum computation, A control unit (102) for providing the plurality of control signals (104) to the plurality of quantum computing units, A signal distribution device (103) for transmitting the plurality of control signals (104) generated from the control unit (102) to the plurality of quantum computing units (101), wherein the signal distribution device (103) is configured to distribute each control signal of the plurality of control signals (104) generated from the control unit (102) to each of the plurality of quantum computing units (101). The control unit (102) is configured to cause each quantum computing unit in the plurality of quantum computing units (101) to execute a separate instance of the quantum computation via the plurality of control signals (104) and the signal distribution device (103), and the signal distribution device (103) is configured to do so. The at least one output signal (106) is acquired from each quantum computing unit in the plurality of quantum computing units (101). Based on the output signal (106), at least one statistical operation is performed to obtain a comprehensive quantum computation result. It comprises a reading unit (105) configured as follows: Apparatus (100), wherein the output signals from the plurality of quantum computing units (101) are time-multiplexed, and the readout unit (105) is further configured to acquire the output signals from each of the plurality of quantum computing units (101) in accordance with the time-multiplexing.

2. The apparatus (100) according to claim 1, wherein each quantum computing unit in the plurality of quantum computing units (101) corresponds to a quantum processing unit (QPU), a core in a multicore QPU, or a subunit of a QPU.

3. The apparatus (100) according to claim 1 or 2, wherein the signal distribution device (103) is configured to distribute each control signal in the plurality of control signals (104) generated from the control unit (102) to each quantum computing unit in the plurality of quantum computing units (101) using at least one T-junction, at least one power distributor, at least one Wilkinson power distributor, at least one directional coupler and / or at least one hybrid coupler.

4. The apparatus (100) according to any one of claims 1 to 3, further comprising a tuning device configured to adjust the characteristics of at least one of the plurality of control signals distributed by the signal distribution device, wherein the at least one characteristic includes at least one of frequency, amplitude, phase and / or relative timing.

5. The apparatus (100) according to claim 4, further comprising at least one voltage-controlled attenuator configured to adjust at least one of the plurality of control signals distributed by the signal distribution device.

6. The apparatus (100) according to claim 5, wherein the at least one voltage-controlled attenuator comprises at least one high-electron-mobility transistor, at least one tuneable reactive impedance element, at least one superconducting quantum interference device and / or at least one varactor diode.

7. The apparatus (100) according to any one of claims 1 to 6, further comprising a delay line coupled to the plurality of quantum computing units (101) and configured to time-multiplex the output signals (106) from the plurality of quantum computing units.

8. The apparatus (100) according to any one of claims 1 to 7, wherein the reading unit (105) further comprises an adder, and the reading unit (105) is configured to perform the at least one statistical operation based on the output signal (106) by coherently adding the output signal (106) via the adder.

9. The apparatus (100) according to any one of claims 1 to 8, wherein each quantum computing unit in the plurality of quantum computing units (101) further comprises a plurality of frequency tuning elements configured to tune the qubit frequencies of the plurality of qubits according to a frequency tuning signal.

10. The apparatus (100) according to any one of claims 1 to 9, wherein each quantum computing unit in the plurality of quantum computing units (101) further comprises a plurality of capacitive tuning elements configured to tune the capacitance of the plurality of qubits according to a capacitive tuning signal.

11. The apparatus (100) according to any one of claims 1 to 10, wherein the plurality of qubits (405) comprises superconducting qubits.

12. The apparatus (100) according to any one of claims 1 to 11, wherein the at least one statistical operation includes at least one of mean, variance and / or cross-entropy.

13. The apparatus (100) according to any one of claims 1 to 12, further comprising a cryostat, wherein the plurality of quantum computing units (101) and the signal distribution device (103) are arranged inside the cryostat.

14. A quantum computing system comprising a plurality of devices (100) according to any one of claims 1 to 13.

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