Quantum memristor system, operation method, quantum computing system and storage medium

Abstract

The invention discloses a quantum memristor system, an operation method, a quantum computing system and a storage medium, and relates to the technical field of quantum computing. The quantum memristor system comprises an ion trapping module, a quantum state initial module, a quantum state regulation and control module and a quantum state reading module, an adopted trapping ion ground state has a hyperfine energy level structure, and clock state transition can be formed between a first energy level and a second energy level in the hyperfine energy level structure. The write-in operation is that microwave pulses are applied to the trapped ions to completely or partially transfer the population from a first energy level to a second energy level, and radio frequency pulses are applied while or after the write-in operation to completely or partially transfer the population of the second energy level to a third energy level to realize state mixing and memory; according to the quantum memristor, the energy level control architecture of the quantum memristor is constructed by adopting the full ground state energy level of trapping ions, rapid decoherence introduced by excited state spontaneous radiation is avoided, and the quantum memristor is insensitive to magnetic field noise, good in stability and long in memory time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of quantum computing, and in particular to a quantum memristor system, an operation method, a quantum computing system and a storage medium. BACKGROUND

[0002] With the gradual slowing down of Moore's law, the traditional computing mode based on the Von Neumann architecture faces the bottleneck of "memory wall" and "power wall" when processing big data and artificial intelligence tasks. In order to break through this bottleneck, the academic and industrial circles are actively exploring new computing paradigms, among which neuromorphic computing and quantum computing are two promising frontiers. Neuromorphic computing simulates the structure and working principle of the biological brain, and integrates storage and computing together, in order to realize more efficient and lower power intelligent computing. Quantum computing utilizes quantum superposition and quantum entanglement, and can provide much more computing power than classical computers in large number factorization and quantum simulation. Quantum memristor is an extension of classical memristor in the quantum field, and is an open-loop quantum system. Its state evolution not only depends on the current input, but also depends on the history of its internal state, thus showing memory effect and nonlinear dynamics. The characteristics of quantum memristor make it possible to combine the advantages of neuromorphic computing and quantum computing, and become a key device for future more powerful computing intelligence.

[0003] Trapped ions have great potential in the implementation scheme of quantum memristor due to their rich energy levels and mature control technology. The core principle of memristor is "history influences future" and "input-output hysteresis". In the three-level or multi-level system of trapped ions, the trapped ions can be driven to undergo Rabi oscillation between the ground state energy level and the excited state energy level by applying an input pulse. After one evolution period, the population of the system in a certain specific energy level (such as the excited state) is measured. This measurement result will be fed back to the input parameter of the next evolution period, for example, if the ion is measured to be in the excited state with a high probability, the intensity of the driving laser can be reduced in the next stage. This "future" operation depending on the "past" measurement result constitutes the memory of the system (similar to the resistance of the traditional memristor depending on the past current), and the output of the system can be made to have a hysteresis response to the input by decaying the excited state population to a metastable state with a variable probability. However, the excited state and metastable state used in the existing three-level or multi-level system usually have a short lifetime. The spontaneous emission of the excited state and metastable state will introduce uncontrollable decoherence, which limits the coherent evolution and memory fidelity of the system. In addition, if the selected energy levels are sensitive to external magnetic fields and other environmental noise, the energy difference between the energy levels will drift, causing the driving laser or microwave field to be detuned, thereby reducing the control fidelity and stability of the memristor performance. SUMMARY

[0004] The present application aims to utilize the characteristics of super-fine structure and super-long life of ground state energy level of trapped ions to construct a quantum memristor system with good coherence, high stability and reliability.

[0005] The quantum memristor system provided by the present application comprises:

[0006] An ion trapping module is provided with at least one trapped ion; the trapped ion is bound in an ion trap in a vacuum environment and is in a millikelvin temperature range; the ground state of the trapped ion comprises a first energy level manifold and a second energy level manifold with different total angular momenta; the first energy level manifold comprises a first energy level, and the second energy level manifold comprises a plurality of Zeeman sub-energy levels split under a preset static magnetic field; wherein the Zeeman sub-energy levels with the same magnetic quantum number as the first energy level are recorded as the second energy level, and the other Zeeman sub-energy levels are recorded as the third energy level; the transition of the trapped ion between the first energy level and the second energy level is a clock state transition;

[0007] A quantum state initial module is configured to generate a pump laser, and the pump laser is configured to transfer the population number of the trapped ion to the first energy level;

[0008] A quantum state regulation module is configured to generate an electromagnetic pulse, and the quantum state regulation module comprises a writing module and a state mixing module; the writing module is configured to generate a microwave pulse, and the microwave pulse is configured to drive the trapped ion to form a Rabi oscillation between the first energy level and the second energy level; the state mixing module is configured to generate a radio frequency pulse, and the radio frequency pulse is configured to drive the trapped ion to form a Rabi oscillation between the second energy level and the third energy level;

[0009] A quantum state reading module is configured to read the population number of the trapped ion in the first energy level or the second energy level.

[0010] Optionally, the trapped ion is 171 Yb + ion, 43 Ca + ion, 87 Sr + ion or 137 Ba + ion.

[0011] Optionally, the trapped ion is 171 Yb + ion, 171 Yb + The ground state of the ion is 2 S 1 / 2, the total angular momentum of the first energy level manifold is F=0, the first energy level is denoted as |0>, the total angular momentum of the second energy level manifold is F=1, the second energy level is denoted as |2>, and the third energy level includes two sub-energy levels denoted as |1> and |3> respectively; the radio frequency pulse is configured to drive the trapped ion to perform Rabi oscillation between the energy level |2> and the energy level |1>, and / or the radio frequency pulse is configured to drive the trapped ion to perform Rabi oscillation between the energy level |2> and the energy level |3>.

[0012] The quantum memristor system provided by the application is operated through the following method steps:

[0013] S1, initialization operation: using a first laser with a preset frequency and polarization state to transfer the population of the trapped ion to the first energy level;

[0014] S2, write-in and state mixing operation: applying a microwave pulse with a preset frequency, amplitude and duration to the trapped ion to transfer part or all of the population of the trapped ion in the first energy level to the second energy level; the amplitude or duration of the microwave pulse is defined as an input signal;

[0015] At the same time or after applying the microwave pulse, at least one radio frequency pulse with a preset frequency, amplitude and duration is applied to the trapped ion to transfer part or all of the population of the trapped ion in the second energy level to the third energy level; for different input signals, the radio frequency pulse is configured to have different amplitudes or durations;

[0016] S3, read operation: reading the population of the trapped ion in the first energy level or the second energy level as an output signal.

[0017] Optionally, the amplitude of the microwave pulse is unchanged each time the write-in and state mixing operation is performed, and the change of the input signal is realized by adjusting the duration of the microwave pulse.

[0018] Optionally, the duration of the microwave pulse is unchanged each time the write-in and state mixing operation is performed, and the change of the input signal is realized by adjusting the amplitude of the microwave pulse.

[0019] Optionally, the third energy level of the trapped ion includes N sub-energy levels, and n radio frequency pulses with different polarization states are sequentially applied to the trapped ion at the same time or after applying the microwave pulse, 1≤n≤N and n is an integer; each radio frequency pulse with a specific polarization state is used to drive the trapped ion to transfer part or all of the population in the second energy level to a specific sub-energy level of the third energy level.

[0020] Optionally, the read operation adopts a state-resolved fluorescence method, which specifically includes the following steps:

[0021] S31, a second laser is applied to the trapped ion after the write and state mixing operation, and the second laser is configured to make the trapped ion transition from a second energy level manifold of the ground state to a preset excited state energy level;

[0022] S32, the probabilities of the bright state and the dark state of the trapped ion are counted by a photodetector.

[0023] The application further provides a quantum computing system composed of the quantum memristor system, the quantum computing system comprising a plurality of ion traps, each ion trap being provided with a plurality of trapped ions; the plurality of trapped ions in each ion trap are coupled to form a one-dimensional ion chain through a shared phonon mode; the plurality of one-dimensional ion chains are coupled to form a neuromorphic topology through a photonic interface; and each trapped ion is controlled through the operation method of the quantum memristor system.

[0024] The application further provides a computer readable storage medium storing a computer program, the computer program being executed by a processor to implement the steps of the operation method of the quantum memristor system.

[0025] The application has the following beneficial effects:

[0026] The quantum memristor system provided by the application adopts trapped ions with hyperfine energy level structures in the ground state, and a clock state transition can be formed between the first energy level and the second energy level in the hyperfine energy level structure of the trapped ions. The write operation of the quantum memristor is performed by transferring the population from the first energy level to the second energy level by applying a microwave pulse to the trapped ions in whole or in part. At the same time or after the write operation, an RF pulse is applied to transfer the population of the second energy level to the third energy level in whole or in part to realize state mixing and memory. The application constructs an energy level control architecture of the quantum memristor using all the energy levels in the ground state, fully utilizes the long lifetime characteristics of the ground state energy level, and avoids the rapid decoherence introduced by the spontaneous emission of the excited state in the traditional scheme. In addition, the quantum memristor system provided by the application selects the first energy level and the second energy level that can form a clock state transition as the core operating energy level (write operation) of quantum state regulation, so that the quantum memristor is not sensitive to magnetic field noise, has good stability, and has a long memory time (up to seconds). BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0028] Figure 1A structural block diagram of a quantum memristor system in some embodiments of the present application;

[0029] Figure 2 A flow chart of an operating method of a quantum memristor system in some embodiments of the present application;

[0030] Figure 3 A structural block diagram of a quantum memristor system in some embodiments of the present application 171 Yb + ions 2 S 1 / 2 A schematic diagram of a ground state hyperfine level structure;

[0031] Figure 4 An input (I)-output (V) hysteresis curve in a theoretical simulation embodiment of the present application;

[0032] Figure 5 A time-population change curve of each level in a theoretical simulation embodiment of the present application;

[0033] Figure 6 A time-variable M change curve in a theoretical simulation embodiment of the present application. DETAILED DESCRIPTION

[0034] In order to make the inventive purposes, features and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the embodiments described below are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0035] Unlike classical memristors (such as ion migration type memristors) which rely on carrier transport, the essence is the correlation between conductance and historical input charge quantity, that is, the current resistance state depends on the past electrical input, and this "memory" can still be retained after power-off; unlike classical memristors, quantum memristors use the microscopic state (energy level, superposition state) of a quantum system to achieve memory, without relying on macroscopic structure reconstruction (such as ion transfer, phase change), the evolution speed of quantum state is much faster than the classical charge transport process, and the quantum system is small in size, and is more easily integrated at high density.

[0036] Trapped ions are quantum bit carriers with mature technology in the field of quantum computing, and their advantages lie in super-long quantum coherence time and atomic-level precise control; the mainstream trapped ion technology is divided into two categories, one is to use a radio frequency alternating electric field to generate a dynamic binding force to bind ions in a Paul trap, and the other is to combine a static magnetic field and a static electric field to bind ions in a Penning trap; the trapped environment of the ions needs to be maintained in ultra-high vacuum (10 -11Superconducting quantum circuit (SQC) and ultra-low temperature (milli-Kelvin, 1mK~100mK) are used to suppress thermal noise and collision noise, and ensure the stability of memory.

[0037] The energy level of an atom or ion is not a single energy level, but is gradually split with the degree of interaction: the first split is determined by the principal quantum number n and the angular quantum number l, corresponding to the shell and subshell of the electron outside the nucleus; the second split is caused by the spin-orbit coupling of the electron, which splits the energy level corresponding to each angular quantum number l into a fine structure corresponding to the total angular momentum quantum number; the third split is the hyperfine energy level structure caused by the magnetic dipole interaction between the atomic nucleus and the electron; the hyperfine energy level structure is directly related to the intrinsic property of the atomic nucleus (nuclear spin) and is hardly affected by the external environment.

[0038] Under the action of an applied static magnetic field, an energy level of an atom or ion can be split into multiple sub-energy levels with slightly different energies due to the Zeeman effect, which is essentially the removal of energy level degeneracy caused by the spatial quantization of the total angular momentum F in the direction of the magnetic field. The prerequisite for this is that the total angular momentum F is non-zero, and the energy level splitting is based on the discrete values of the magnetic quantum number, so one original energy level will be split into 2F+1 Zeeman sub-energy levels. The energy level spacing of the Zeeman sub-energy levels is proportional to the magnetic field strength, and the transition frequency between the Zeeman sub-energy levels can be adjusted by adjusting the Zeeman sub-energy level spacing.

[0039] Other professional terms related to the embodiments of the present application are explained as follows:

[0040] Quantum superposition state: A quantum system (e.g. the energy level of a trapped ion) can be in a linear superposition of multiple eigenstates, and this superposition is a quantum-specific probability amplitude superposition.

[0041] Population: A physical quantity that describes the number distribution of particles in different quantum states, which is essentially a probability statistical value of particles in a particular energy level.

[0042] Clock state transition: A transition with zero first-order derivative of magnetic field; in a specific static magnetic field (typical value between 10-1000 μT), the first-order term of the Zeeman effect between two energy levels is eliminated by using the precise matching of the magnetic quantum number and the Lande factor, so that the transition frequency between the two energy levels is not sensitive to the small fluctuations of the magnetic field, thereby ensuring the long-term stability of the transition and the ultra-long coherence time; the atomic energy level that can form a clock state transition is usually used as a reference for the "time scale" and is widely studied and applied in the field of quantum atomic clocks.

[0043] Optical pumping: the interaction of light of a specific frequency with the energy levels of atoms, ions or molecules in resonance, which can excite particles from low-energy levels (ground state or low excited state) to high-energy levels, thereby achieving particle number population control (such as particle number inversion, specific energy level enrichment); combined with resonance absorption and spontaneous emission, particles fall directly from high-energy levels to the ground state, or first jump to an intermediate excited state and then fall to the ground state. Optical pumping technology can pump all the population of one ion to the ground state.

[0044] Rabi oscillation: the periodic and coherent transition between two energy levels of a quantum system driven by a specific electromagnetic field, which is one of the core basic effects in the field of quantum optics and quantum control. The essence is the periodic superposition and evolution of quantum states under the action of the driving field. The frequency of the electromagnetic field should satisfy the resonance condition hν=ΔE (h is the Planck constant and v is the driving field frequency) with the energy difference ΔE between the two energy levels. At this time, the wave function will present a superposition state, and the wave function satisfies:

[0045] ;

[0046] where , represent two energy levels, and the corresponding population is |α| 2 and |β| 2 , respectively. |α| 2 =cos 2 (Ωt / 2), |β| 2 =sin 2 (Ωt / 2), |α| 2 +|β| 2 =1.

[0047] State-resolved fluorescence technology: through precise differentiation of the characteristic fluorescence signals (such as fluorescence wavelength, intensity, polarization state or time evolution) corresponding to different quantum states, selective detection of a single quantum state is achieved.

[0048] Ground state: the lowest energy level corresponding to the electronic configuration of a particle, and there is no lower energy level for spontaneous emission of electrons, so the superposition quantum state of the ground state has a significantly longer lifetime than the excited state.

[0049] Energy level manifold: a collection of energy levels with certain common characteristics in a quantum system.

[0050] Coherence and decoherence: in this invention, coherence refers to the state in which quantum properties (such as specific quantum superposition states) are maintained; decoherence refers to the loss of quantum properties (such as the degradation of a certain quantum superposition state to a classical probabilistic state).

[0051] The technical scheme of the present application is based on mature manipulation technology of trapped ions, stability and long life characteristics of ground state energy level, and super-fine energy level structure existing in the ground state, and constructs a quantum memristor system with good coherence, high stability and reliability.

[0052] Referring to Figure 1 In some embodiments, the present application provides a quantum memristor system comprising an ion trapping module, a quantum state initial module, a quantum state control module and a quantum state reading module.

[0053] The ion trapping module is provided with at least one trapped ion; the trapped ion is bound in an ion trap (Paul trap or Penning trap) in a vacuum environment and is in a millikelvin temperature zone (1mK~100mK).

[0054] In the embodiment of the present application, due to the quantum superposition characteristics of the trapped ion, one trapped ion can satisfy the energy level construction of a single quantum memristor, and the physical structure is compact; the ground state of the trapped ion includes a first energy level manifold and a second energy level manifold with different total angular momenta; the first energy level manifold contains a first energy level, and the second energy level manifold contains a plurality of Zeeman sub-energy levels split under a preset static magnetic field; wherein the plurality of Zeeman sub-energy levels with the same magnetic quantum number as the first energy level are recorded as the second energy level, and the other Zeeman sub-energy levels are recorded as the third energy level; the transition of the trapped ion between the first energy level and the second energy level is a clock state transition, which can maximize the coherence time of the system, reduce the sensitivity to environmental magnetic field noise, and realize more stable and reliable memristor behavior.

[0055] It can be understood that the ion trapping module includes a magnetic field device for generating an ion trap, an electric field device, and a Doppler cooling device or a resonance laser cooling device for cooling ions; these devices have been widely studied in the field of trapped ion technology and have mature and standard implementation methods, and those skilled in the art can implement the technical scheme of the embodiment of the present application according to the existing related devices and technologies in the field of trapped ions.

[0056] The quantum state initial module is used to generate pump laser, and the pump laser is configured to transfer the population number of the trapped ion to the first energy level; specifically, the particles are excited from a low excited state to a preset high energy level or an intermediate excited state by the pump laser, and then the particles spontaneously radiate back to the first energy level of the lowest energy state.

[0057] The energy difference between the first energy level and the second energy level of the ground state of the trapped ion is usually in the microwave band (GHz order of magnitude), and the energy difference between the second energy level and the third energy level is usually in the radio frequency band (MHz order of magnitude); the quantum state regulation module is used for generating electromagnetic pulses, including a write-in module and a state mixing module; the write-in module is used for generating microwave pulses, and the microwave pulses are configured to drive the trapped ion to perform Rabi oscillation between the first energy level and the second energy level; the state mixing module is used for generating radio frequency pulses, and the radio frequency pulses are configured to drive the trapped ion to perform Rabi oscillation between the second energy level and the third energy level; specifically, the polarization-adjustable radio frequency pulses can be generated by two groups of mutually orthogonal coils.

[0058] The quantum state reading module is used for reading the population number of the trapped ion at the first energy level or the second energy level.

[0059] Referring to Figure 2 , the quantum memristor system proposed in the embodiment of the present application is operated through steps S1-S3:

[0060] S1, initialization operation: the population number of the trapped ion is all transferred to the first energy level by using a first laser with a preset frequency and a polarization state; this step prepares the ion to the initial state with high fidelity through optical pumping technology.

[0061] S2, write-in and state mixing operation: a microwave pulse with a preset frequency, amplitude and duration is applied to the trapped ion, and part or all of the population number of the trapped ion at the first energy level is transferred to the second energy level; the amplitude or duration of the microwave pulse is defined as an input signal; at the same time or after the microwave pulse is applied, at least one radio frequency pulse with a preset frequency, amplitude and duration is applied to the trapped ion, and part or all of the population number of the trapped ion at the second energy level is transferred to the third energy level; for different input signals, the radio frequency pulse is configured to have different amplitudes or durations.

[0062] In the embodiment of the present application, the input signal can be changed in two ways: one, the amplitude of the microwave pulse is unchanged when the quantum memristor system performs the write-in and state mixing operation each time, and the input signal is changed by adjusting the duration of the microwave pulse; two, the duration of the microwave pulse is unchanged when the quantum memristor system performs the write-in and state mixing operation each time, and the input signal is changed by adjusting the amplitude of the microwave pulse.

[0063] In some specific embodiments, the third energy level of the trapped ion includes N sub-energy levels, and n polarization state different radio frequency pulses are sequentially applied to the trapped ion at the same time or after the microwave pulse is applied, n≤N and n is an integer; each specific polarization state radio frequency pulse is used to drive part or all of the population number of the trapped ion at the second energy level to be transferred to a specific sub-energy level in the third energy level.

[0064] S3, read operation: read the population number of the trapped ion at the first energy level or the second energy level as an output signal.

[0065] Specifically, the quantum memristor system read operation can adopt a state-resolved fluorescence method, including the steps of:

[0066] S31, a second laser is applied to the trapped ion after the write and state mixing operation, and the second laser is configured to make the trapped ion transition from the second energy level manifold of the ground state to a preset excited state energy level.

[0067] S32, the probabilities of the bright state and the dark state of the trapped ion are counted by a photodetector; the types of the photodetector include but are not limited to a photomultiplier tube (PMT), a silicon photomultiplier (SiPM), a charge-coupled device (CCD), a complementary metal-oxide image sensor (CMOS), an avalanche photodiode (APD), and the like.

[0068] In the embodiment of the present application, step S2 is the core step to realize the history dependence of the quantum memristor. First, a microwave pulse is applied to perform a write operation, and the write operation transfers the population number of the trapped ion from the first energy level to the second energy level entirely or partially according to the input signal parameters; a radio frequency pulse is applied to perform a state mixing operation, and the state mixing operation transfers the population number of the second energy level to the third energy level entirely or partially; each write operation is changed by the state mixing operation, and the effect of the next write operation depends on the population number difference between the first energy level and the second energy level after the previous write operation and the influence of the state mixing operation. Therefore, the response of the system to the current input signal depends on the evolution history of the internal state of the system, that is, the system has the characteristic of the memristor that "history affects future".

[0069] In the embodiment of the present application, the write operation of each microwave pulse pumps different population numbers to the second energy level, and the radio frequency pulse is configured to have different amplitudes or durations for different input signals; for example, when the amplitude of the microwave pulse is continuously increased, more population numbers are pumped to the second energy level by each microwave write operation, and the population numbers are further dispersed to the third energy level by the radio frequency pulse, and the corresponding radio frequency pulse parameters are different for each microwave write operation (similar to the different resistance values corresponding to different currents in a traditional memristor); even if the amplitude of the microwave pulse is continuously reduced, the population numbers stored in the third energy level will be leaked back to the second energy level with different probabilities through the radio frequency pulse, which will affect the population number distribution of the first energy level and the second energy level, which will cause the return path of the input-output signal of the system to be different from the initial path, thereby forming a hysteresis curve in the coordinate system plane of the input-output signal, that is, the system has the characteristic of the memristor that "input-output hysteresis".

[0070] The existence of the two core characteristics of "history affects future" and "input-output hysteresis" proves that the quantum memristor system constructed by the present application has a memristor behavior.

[0071] Compared with the scheme of constructing a quantum memristor by using an excited state energy level, the quantum memristor system provided in the embodiment of the application utilizes the hyperfine energy level structure of a trapped ion ground state to construct an energy level operation architecture of the quantum memristor. The ground state energy level has a long lifetime characteristic compared with the excited state energy level, thereby avoiding the rapid decoherence introduced by spontaneous emission of the excited state in the traditional scheme. In addition, the quantum memristor system provided in the embodiment of the application selects a first energy level and a second energy level that can form a clock state transition as core operation energy levels (write operation) of quantum state regulation, so that the quantum memristor is not sensitive to magnetic field noise, has good stability, and has a memory time of tens of milliseconds to seconds (the memory time corresponding to different trapped ions is different), which is much longer than that of the traditional scheme.

[0072] In addition, the prior art relies on frequent quantum measurement and subsequent classical feedback control. Since quantum measurement itself has a projection property, that is, quantum measurement will cause the system to collapse from a superposition state to a certain determined eigenstate, the quantum superposition state information of the system is destroyed (equivalent to emptying the superposition state information before each measurement), meanwhile, the introduction of the classical feedback loop increases the overall complexity and delay of the system, and can introduce additional noise and error sources. In the quantum memristor system provided in the embodiment of the application, the microwave pulse and the radio frequency pulse are configured to cause the trapped ion to undergo a Rabi oscillation between energy levels. The Rabi oscillation is a kind of coherent evolution, which is real-time and continuous. The preset input signal and radio frequency pulse parameters will make the system evolve along a preset path, that is, a specific input signal corresponds to a specific output signal. For example, if it is detected that the system is in a superposition state A, it can be known that the input is a microwave pulse a1 and a radio frequency pulse a2, and vice versa. Therefore, the information can be designed by pre-controlling the input signal and the radio frequency pulse parameter, and the output signal can be obtained according to the input signal and the coded information, without the need for quantum measurement of each output signal, so that the dependence on the complex and slow measurement-feedback loop can be reduced, and the quantum memristor can run faster and be controlled more simply.

[0073] In some preferred embodiments, the trapped ion can be selected from 171 Yb + ion, 171 Yb + The trapped ion has a natural, inherent and completely isotopic ground state hyperfine energy level structure, has natural stability and consistency, and 171 Yb + The coherence operation technology of the trapped ion is relatively mature, and the fidelity of the single-bit gate and the double-bit gate has reached an extremely high level (> 99%) in the existing research, which can ensure the accuracy and repeatability of the state evolution of the quantum memristor.

[0074] Referring to Figure 3 , 171 Yb+ The nuclear spin I = 1 / 2 of the ion is coupled with the total angular momentum J = 1 / 2 of the electron to form a ground state with a hyperfine structure of 2 S 1 / 2 The ground state structure is split into two hyperfine energy level manifolds: an F = 0 manifold with a total particle angular momentum F = 0, containing one magnon energy level |0> (magnetic quantum number m F = 0); and an F = 1 manifold with a total particle angular momentum F = 1, which is split into three magnon energy levels |1> (magnetic quantum number m F = -1), |2> (magnetic quantum number m F = 0), and |3> (magnetic quantum number m F = +1) under a weak static magnetic field (the specific value satisfies the Zeeman effect); the energy level |0> is taken as a first energy level, the energy level |2> is taken as a second energy level, and the energy levels |1> and |3> are taken as third energy levels; wherein the transition between the energy level |0> and the energy level |2> is a clock state transition insensitive to a first-order magnetic field, has a coherence time of seconds, and can make the memory time of the quantum memristor reach seconds; a microwave pulse is configured to drive 171 Yb + ions to form Rabi oscillation between the energy level |0> and the energy level |2>; and a radio frequency pulse is configured to drive 171 Yb + ions to form Rabi oscillation between the energy level |2> and the energy level |1> and / or the energy level |3>; wherein and can be realized by radio frequency driving in different polarization states (sigma - polarization or sigma + polarization).

[0075] Taking the three energy levels |0>, |2>, and |1> of the 171 Yb + ion as an example, the specific explanation of the technical principle of the application is as follows in combination with mathematical reasoning and software simulation:

[0076] Resonant microwave (the microwave frequency is equal to the gap between two energy levels) is used to drive 171 Yb + ions to form Rabi oscillation between the energy level |0> and the energy level |2>; resonant radio frequency is used to drive 171 Yb + ions to form Rabi oscillation between the energy level |2> and the energy level |1>; the frequency of the Rabi oscillation is , wherein is a magnetic dipole moment, is a magnetic induction amplitude, is a Planck constant.

[0077] Suppose that the initial state is , then in Under the action of resonant microwave, the energy level The population is cos 2 (Ωt / 2), the energy level The population is sin 2 (Ωt / 2), 171 Yb + ion is in the superposition state of energy level and energy level By changing the duration t of the microwave pulse or changing the amplitude (electric field strength or magnetic induction strength) of the microwave pulse, the population of energy level and energy level can be controlled, that is, the transition probability of can be controlled.

[0078] Next, take changing the duration t of the microwave pulse as an example, and couple |0〉, |2〉, |1〉 three energy levels through microwave pulse and radio frequency pulse.

[0079] Step 1, write operation:

[0080] Apply a microwave pulse with a frequency close to 12.642GHz and a preset duration, and prepare the quantum state of 171Yb + ion as:

[0081] ;

[0082] In the formula, α and β are complex numbers, and the input signal I is defined as the population of state after this step is executed (usually the parameters of the microwave pulse are used as the input signal, and here the population of state is used as the input signal for the convenience of subsequent mathematical analysis, and the population of state and the parameters of the microwave pulse are one-to-one correspondence):

[0083] ;

[0084] Step 2, state mixing operation:

[0085] Apply a radio frequency pulse at the same time or after applying the microwave pulse to drive energy level , this step will further distribute the population of state to state , and the quantum state of 171Yb + ion is updated as:

[0086] ;

[0087] Define the output signal V as the population of state after this step is executed:

[0088] ;

[0089] Therefore, the input signal and the output signal satisfy the relationship: .

[0090] The relationship is similar to the relationship between the current and the voltage in a conventional memristor, which is equivalent to the resistance of a conventional memristor; define M , which can be adjusted in experiments, similar to the input microwave pulse, only the amplitude or the action time of the radio frequency pulse needs to be adjusted to change the value of M; taking the action time of the radio frequency pulse as an example, M=M(t), M(t) satisfies:

[0091] ;

[0092] In the formula, dq represents the change amount of the input signal I in a unit time dt; for simplicity, only the linear relationship between M and q is considered, and dM / dq=A is defined, where A is a constant.

[0093] Therefore, the value of M satisfies dM=A·I·dt at each time of updating the value of M.

[0094] Since the input signal I satisfies the Rabi oscillation, only the action time of the microwave pulse needs to be changed from 0 to T π (T π represents the time of one period), I can traverse from 0 to 1; correspondingly, for different input signals I, the value of M is different, which is equivalent to the different resistance values corresponding to different currents in a conventional memristor, and this condition is the key to realizing the input-output hysteresis behavior, and dt represents the frequency of updating the value of M.

[0095] In some embodiments, A=0.004, T π =200μs, and dt=3μs, the input-output signals of the quantum memristor are theoretically simulated, and the simulation results are shown in Figures 4-6 .

[0096] Referring to Figure 6 , Figure 6 , the curve of M evolving with time is set, M increases with time, but the increasing rate first increases and then gradually slows down; referring to Figure 5 , Figure 5 , the change of the population numbers of |0>, |1>, and |2> during time 0-T π , the population number of |0> continuously decreases in the initial stage, which corresponds to the continuously increasing input signal, M continuously increases and the rate becomes faster and faster, which means that a large number of population numbers flow into |1>, M and I are both increasing, and according to V=M·I, the output signal V( Figure 5The population of |2> reaches the maximum actually lags behind the maximum of I; during the decreasing stage of the input signal I, M is still increasing but the rate gradually slows down, at this time the population of |2> will continue to slowly increase for a period of time to reach the maximum, then the population of |2> gradually decreases until 0; setting the change step of M as dt=3μs, the evolution process of I-V as shown in FIG. 2 can be seen, which shows that the evolution of I-V presents an obvious hysteresis curve, verifying the memristive effect of the system. Figure 4

[0097] Based on the above embodiment, in order to completely illustrate the implementation process and application value of the technical scheme of the present application, the present application further proposes the following specific embodiments, it should be noted that the following specific embodiments are only exemplary in nature and do not limit the scope of protection of the present application in any form.

[0098] Embodiment 1

[0099] An 171 Yb + ion is used as a trapped ion, and the |0>, |1>, |2>, and |3> four energy levels of the ground state hyperfine energy level structure of the Yb ion are used to construct a quantum memristor. 171 Yb +

[0100] Step 1, initialization operation: a laser with a wavelength of 369.5nm, a specific frequency and a polarization is applied by using optical pumping technology to pump the trapped ion to the |0> state with high fidelity.

[0101] Step 2, write-in and state mixing operation: the write-in operation is performed on the 171 Yb + ion by applying a microwave pulse with a frequency close to 12.642GHz, which couples the |0> state and the |2> state, so that the Yb ion forms a Rabi oscillation between the |0> energy level and the |2> energy level, and the input signal is defined as the amplitude of the microwave pulse. 171 Yb +

[0102] ​​​State mixing operation, a preset amplitude of RF pulse is applied to transfer all or part of the population of energy level |2> to energy level |1>; or, a preset amplitude of RF pulse is applied to transfer all or part of the population of energy level |2> to energy level |3>; or, a preset amplitude of RF pulse is first applied to transfer part of the population of energy level |2> to energy level |1>, and then a polarization state different from the first one of preset amplitude of RF pulse is applied to transfer all or part of the remaining population of energy level |2> to energy level |3>, for example, a π / 2 pulse (π / 2 refers to the rotation angle θ of the pulse, θ = ∫Ω(t)dt, Ω is the Rabi frequency) can be first applied to transfer part of the population of energy level |2> to energy level |1>, and then a π pulse with different polarization state is applied to transfer all of the remaining population of energy level |2> to energy level |3>.

[0103] Step 3, readout operation: realized by the mature state-resolved fluorescence method, the final population of energy level |0> is read out after the write-in and state mixing operations. 171 Yb + The ion is driven by a 369.5 nm laser with a specific frequency and polarization. 171 Yb + The ion is driven by a 369.5 nm laser with a specific frequency and polarization. 2 P 1 / 2 The ion is driven by a 369.5 nm laser with a specific frequency and polarization. 171 Yb + The ion is driven by a 369.5 nm laser with a specific frequency and polarization. 171 Yb + The ion is driven by a 369.5 nm laser with a specific frequency and polarization.

[0104] Example 2

[0105] The quantum memristor constructed in this embodiment fixes the amplitude of microwave and radio frequency, and changes the input signal by changing the duration; this embodiment is designed with reference to embodiment 1, the difference is that in step 2, the input signal is defined as the duration of the microwave pulse; in the state mixing operation, a radio frequency pulse with a preset duration is applied to transfer all or part of the population of the energy level |2> to the energy level |1>; alternatively, a radio frequency pulse with a preset duration is applied to transfer all or part of the population of the energy level |2> to the energy level |3>; alternatively, a radio frequency pulse with a preset duration is first applied to transfer part of the population of the energy level |2> to the energy level |1>, and then a radio frequency pulse with a different polarization state and a preset duration is applied to transfer all or part of the remaining population of the energy level |2> to the energy level |3>.

[0106] Embodiment 3

[0107] Since the trapped ion technology itself has good scalability, based on the quantum memristor system and the operation method thereof proposed in the above embodiments, this embodiment proposes a quantum computing system; the quantum computing system comprises a plurality of ion traps, and each ion trap is provided with a plurality of trapped ions.

[0108] Specifically, in the ion trap, the one-dimensional ion chain forms a "Coulomb crystal" through the balance of the Coulomb repulsion and the trapped electric field, and the collective vibration mode can be quantized as a phonon. The quantum information of ion A is encoded into the phonon mode by applying a spin-dependent force to ion A using Raman laser. The phonon mode can propagate in the one-dimensional ion chain. By adjusting the Raman laser pulse timing, the phonon energy can be transferred from ion A to ion B, and the quantum information of ion A is also transferred to ion B. The one-dimensional ion chain realizes high-speed short-range coupling through the phonon mode, which is used to simulate the synapse of a neural network.

[0109] Further, a plurality of one-dimensional ion chains can be coupled to form a neural topological structure through a photon interface. Specifically, the trapped ions can be efficiently coupled to form an ion-photon entangled state through an electric dipole transition under the excitation of a specific wavelength laser. Ion A and ion C in two different ion traps are prepared into ion-photon entangled states, and the photons input into the beam splitter of the two ion traps are subjected to Hong-Ou-Mandel interference. If the two ion traps are successfully detected by coincidence detection, ion A and ion C enter the entangled state. By combining local operations and classical communication, the quantum logic gate can be transferred from one ion trap to another. Long-range coupling between different ion traps (one-dimensional ion chains) is realized through a photon interface, and a distributed neural network can be constructed.

[0110] The quantum computing system provided in the embodiment takes the quantum memristor system provided in the above embodiment as a physical architecture basis, and performs single trapped ion manipulation through the operation method provided in the above embodiment; therefore, the quantum computing system also has the beneficial effects of the above embodiment; and the devices and control methods required for trapped ion shared phonon mode coupling and one-dimensional ion chain photonic interface coupling have been widely studied in the prior art, and will not be described herein. It should be understood that the quantum computing system constructed by the quantum memristor system and the operation method thereof provided in each embodiment of the present application all belong to the protection scope of the present application.

[0111] The quantum memristor system provided in the embodiment can be used in a quantum computing system 171 Yb + As a trapped ion, as long as the ground state has a hyperfine energy level structure, at least two energy levels in the hyperfine energy level structure can form a clock state transition, such as 43 Ca + ion, 87 Sr + ion, or 137 Ba + ion.

[0112] For the 43 Ca + ion, the 4 S 1 / 2 ground state is split into two energy level manifolds of F=4 and F=3, each of which can be further split into a plurality of Zeeman sub-energy levels under a static magnetic field, and the energy level |F=4, m F =0〉 and the energy level |F=3, m F =0〉 can form a clock state transition and have a long coherence time, and can be used as a core operation energy level of a quantum memristor; 87 Sr + ion, the 5 S 1 / 2 ground state can be split into two energy level manifolds of F=11 and F=10, and the energy level |F=11, m F =0〉 and the energy level |F=10, m F =0〉 can be used as a core operation energy level of a quantum memristor; 137 Ba + ion, the 6 S 1 / 2 ground state has two energy level manifolds of F=2 and F=1, and the energy level |F=2, m F =0〉 and the energy level |F=1, m F =0〉 can be used as a core operation energy level of a quantum memristor.

[0113] The embodiment of the present application also provides a computer readable storage medium for storing a computer program, the computer program being executed by a processor to realize the steps of the quantum memristor system operation method.

[0114] The above embodiments are only used to illustrate the technical solutions of the present application, but not limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A quantum memristor system, characterized in that, include: An ion trapping module is provided with at least one trapped ion; the trapped ion is confined in an ion trap in a vacuum environment and is located in the milliKelvin temperature range; the ground state of the trapped ion includes a first energy level manifold and a second energy level manifold with different total angular momentum; the first energy level manifold contains a first energy level, and the second energy level manifold contains multiple Zeeman sub-levels split into under a preset static magnetic field; wherein, among the multiple Zeeman sub-levels, the one with the same magnetic quantum number as the first energy level is denoted as the second energy level, and the other Zeeman sub-levels are denoted as the third energy level; the transition of the trapped ion between the first energy level and the second energy level is a clock state transition; A quantum state initialization module for generating a pump laser, the pump laser being configured to transfer the population of the trapped ions to a first energy level; A quantum state manipulation module for generating electromagnetic pulses includes a writing module and a state mixing module; the writing module generates microwave pulses configured to drive the trapped ions to form Rabi oscillations between a first energy level and a second energy level; the state mixing module generates radio frequency pulses configured to drive the trapped ions to form Rabi oscillations between a second energy level and a third energy level. A quantum state readout module is used to read the population of the trapped ion at the first or second energy level.

2. The quantum memristor system according to claim 1, characterized in that, The trapped ions are 171 Yb + ion, 43 Ca + ion, 87 Sr + ions or 137 Ba + ion.

3. The quantum memristor system according to claim 1, characterized in that, The trapped ions are 171 Yb + ion, 171 Yb + The ground state of the ion is 2 S 1 / 2 The total angular momentum of the first energy level manifold is F=0, and the first energy level is denoted as |0〉. The total angular momentum of the second energy level manifold is F=1, and the second energy level is denoted as |2〉. The third energy level includes two sub-levels denoted as |1〉 and |3〉, respectively. The radio frequency pulse is configured to drive the trapped ion to form a Rabi oscillation between energy level |2〉 and energy level |1〉, and / or the radio frequency pulse is configured to drive the trapped ion to form a Rabi oscillation between energy level |2〉 and energy level |3〉.

4. A method of operating the quantum memristor system according to any one of claims 1-3, characterized in that, The operation method includes the following steps: S1, Initialization operation: Use a first laser with a preset frequency and polarization state to transfer the population of the trapped ions to the first energy level; S2, Write and State Mixed Operation: Apply a microwave pulse with a preset frequency, amplitude and duration to the trapped ion to transfer part or all of the population of the trapped ion in the first energy level to the second energy level; the amplitude or duration of the microwave pulse is defined as the input signal; Simultaneously or after applying a microwave pulse, at least one radio frequency pulse with a preset frequency, amplitude, and duration is applied to the trapped ions to transfer part or all of the population of the trapped ions located in the second energy level to the third energy level; for different input signals, the radio frequency pulse is configured with different amplitudes or durations; S3, Reading operation: Read the population of the trapped ion at the first or second energy level as the output signal.

5. The method of operating the quantum memristor system according to claim 4, characterized in that, Each time a write and status mixing operation is performed, the amplitude of the microwave pulse remains unchanged, and the input signal is changed by adjusting the duration of the microwave pulse.

6. The method of operating the quantum memristor system according to claim 4, characterized in that, Each time a write and status mixing operation is performed, the duration of the microwave pulse remains unchanged, and the input signal is changed by adjusting the amplitude of the microwave pulse.

7. The method of operating the quantum memristor system according to claim 4, characterized in that, The third energy level of the trapped ion includes N sub-energy levels. At the same time or after the application of the microwave pulse, n radio frequency pulses with different polarization states are sequentially applied to the trapped ion, where 1≤n≤N and n is an integer. Each radio frequency pulse with a specific polarization state is used to drive the trapped ion to transfer part or all of its population at the second energy level to a specific sub-energy level of the third energy level.

8. The method of operating the quantum memristor system according to claim 7, characterized in that, The reading operation employs state-resolved fluorescence, and specifically includes the following steps: S31, apply a second laser to the trapped ion after the write and state mixing operation, the second laser being configured to cause the trapped ion to transition from the ground state second energy level manifold to a preset excited state energy level; S32, use a photodetector to statistically analyze the probabilities of the bright and dark states of the trapped ions.

9. A quantum computing system, comprising the quantum memristor system according to any one of claims 1-3, characterized in that, The quantum computing system includes multiple ion traps, each containing multiple trapped ions; Multiple trapped ions in each ion trap are coupled together to form a one-dimensional ion chain through a shared phonon mode. Multiple one-dimensional ion chains are coupled through a photonic interface to form a neuromorphic topology; Each trapped ion is manipulated by the method of operation of the quantum memristor system according to any one of claims 4-8.

10. A computer-readable storage medium, characterized in that, The system contains a computer program that, when executed by a processor, implements the steps of the method of operating the quantum memristor system according to any one of claims 4-8.

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