A general quantum simulator based on a cold atom system

Abstract

An embodiment of the present invention provides a general quantum simulator based on a cold atom system, which uses the Zeeman magnetic sub-level system of the hyperfine structure of alkali metal atoms to simulate multi-dimensional physical and chemical models. Through the focusing mapping relationship, specific physical and chemical models can be mapped to specific energy levels of atoms. By adjusting the intensity, frequency, and phase of the microwave signal generated by an arbitrary waveform generator, any coupling between two energy levels can be achieved. Combining multiple arbitrary waveform generators can achieve arbitrary control of a multi-dimensional system. According to the control requirements of a specific physical system, the general quantum simulator can be realized by adjusting the microwave signal; it has a universal characteristic and the advantage of not being limited to specific physical and chemical models, and can achieve quantum simulation of any multi-dimensional system. In the current era of rapid development of quantum technology, it has broad application prospects and scientific research value.

Description

Technical Field

[0001] Embodiments of the present invention relate to the technical field of quantum simulation, and particularly to a general quantum simulator based on a cold atom system. Background Art

[0002] In 1982, the famous American physicist Richard P. Feynman conceived a super-powerful calculator relying on the operation of microscopic particles, called a "quantum computer". His central idea was that quantum devices could use the principles of quantum entanglement and quantum superposition to perform operations that classical computers could not. Two new concepts were derived from this idea: quantum computing and quantum simulation. Quantum simulation is to use a controllable quantum system to simulate the quantum system to be studied, and it can be used as an effective experimental means to study problems that are difficult to calculate by classical computers and phenomena that cannot be realized under experimental conditions.

[0003] In the research of condensed matter physics, although brilliant achievements have been made in many aspects, due to the limitations of experimental systems and research methods, there are still many unsolved problems in the field of strongly correlated many-body systems, such as high-temperature superconductivity, quantum magnets, quantum phase transitions, etc. By constructing a quantum simulator, these problems can be experimentally studied. During the quantum simulation process, researchers often care about some critical phenomena, such as the phase transition point. The quantum simulation process does not require high-fidelity quantum manipulation, so it has attracted wide attention. General quantum simulation is to establish a mapping between the research object and the simulator, and use a controllable quantum system to directly simulate the Hamiltonian of the quantum system to be studied. Since the Hamiltonian of the simulation system corresponds to the model Hamiltonian to be simulated, an appropriate projection can be selected according to the problem to be studied to study the dynamic or ground state properties of the system. The most important advantage of general quantum simulation is that it has relatively low requirements for the manipulation accuracy of the simulator and has a certain fault tolerance ability, and can be effective even in the case of errors. Summary of the Invention

[0004] Embodiments of the present invention provide a general quantum simulator based on a cold atom system, which can realize the quantum simulation of specific physical and chemical models by precisely controlling the microwave field frequency and polarization, and has important scientific significance in scientific research and industrial applications.

[0005] In a first aspect, embodiments of the present invention provide a general quantum simulator based on a cold atom system, including a three-dimensional magneto-optical trap, a glass vacuum chamber, an atomic release agent, and a photomultiplier detector;

[0006] The glass vacuum chamber is used to form a closed high-vacuum background environment;

[0007] The atomic release agent is used to release the atoms required by the simulator into the vacuum glass chamber;

[0008] The three-dimensional magneto-optical trap is used to construct a quadrupole magnetic field required for trapping atoms, and trap the atoms at the center of the quadrupole magnetic field to form a cold atom cloud;

[0009] The photomultiplier detector is used to detect atomic fluorescence and extract the evolved atomic information.

[0010] Compared with the prior art, the embodiment of the present invention transforms a complex and difficult-to-implement model into an equivalent quantum model for simulation, and more directly understands its internal mechanism; uses the hyperfine Zeeman magnetic sub-levels of cold atoms for encoding and mapping corresponding specific physical and chemical models. Its properties include: any form of coupling can be achieved by adjusting the microwave intensity, frequency and phase; the atomic energy levels are more stable, and different atomic energy levels are the same under the same environment. Compared with artificial atoms, it has a more stable characteristic.

[0011] Preferably, the three-dimensional magneto-optical trap includes a pair of anti-Helmholtz coils and three pairs of counter-propagating laser beams;

[0012] The anti-Helmholtz coils are used to form a quadrupole magnetic field in the glass vacuum chamber;

[0013] The three pairs of counter-propagating laser beams are irradiated to the center of the coils of the anti-Helmholtz coils, so that the atoms at the coil center are subjected to an optical scattering force pointing everywhere to the coil center to capture and cool the atoms.

[0014] Preferably, the atomic releasing agent is specifically used to perform a reduction reaction and release the alkali metal atoms required by the simulator when heated by an electric current.

[0015] Preferably, it further includes a plurality of microwave horns, and the microwave horns are used to radiate microwave pulses to the cold atom cloud.

[0016] Preferably, it further includes a fixing frame, and the fixing frame is used to fix the glass vacuum chamber and the three-dimensional magneto-optical trap; the vacuum glass chamber is connected to an ion pump through a tee and a corrugated pipe; the ion pump is used to maintain a high vacuum state in the glass vacuum chamber; the gas molecules in the ion pump are efficiently ionized in the electromagnetic field, and the ions bombard the cathode titanium plate under the action of high voltage, splashing out fresh titanium materials and depositing them on the anode cylinder wall to adsorb inert gas molecules.

[0017] Preferably, the pressure in the glass vacuum chamber is not greater than 10 -9 Pa.

[0018] Preferably, the microwave pulse is generated by an arbitrary waveform generator, and the intensity, frequency and phase of the microwave pulse are adjustable.

[0019] Preferably, the tee joint is connected to a mechanical molecular pump, which is used to create a primary vacuum environment in the glass vacuum chamber.

[0020] A general quantum simulator based on a cold atom system provided by an embodiment of the present invention uses a multi-level system of Zeeman magnetic sub-levels of the hyperfine structure of alkali metal atoms to simulate multi-dimensional physical and chemical models. Through the focusing mapping relationship, specific physical and chemical models can be mapped to specific energy levels of atoms. By adjusting the intensity, frequency, and phase of the microwave signal generated by an arbitrary waveform generator, any coupling between two energy levels can be achieved. Combining multiple arbitrary waveform generators can achieve arbitrary control of a multi-dimensional system. According to the control requirements of a specific physical system, the general quantum simulator can be realized by adjusting the microwave signal; using microwave pulses to manipulate atomic clusters, microwaves have a longer wavelength, which can make the field strength felt by atoms more uniform. Therefore, the microwave-based control system has a longer coherence time and can perform more operations; select appropriate atoms for manipulation according to the number of energy levels required by a specific model, and there is a large flexibility in terms of manipulation difficulty; by selecting microwaves with appropriate intensity, frequency, and phase, the manipulation of corresponding energy levels can be achieved. During detection, the ground-state clusters are excited to the excited state, and the relative atomic number of this energy level can be deduced by collecting the fluorescence of spontaneous emission of excited-state atoms. Combining the method of multiple measurements can achieve the measurement of the atomic number of any energy level. The fluorescence normalization detection method has the characteristics of high signal-to-noise ratio and is widely used in cold atom experiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0022] Figure 1 It is a schematic diagram of the principle of simulating a Hopfield neuron by the simulator according to an embodiment of the present invention;

[0023] Figure 2 It is a schematic structural diagram of the quantum simulator according to an embodiment of the present invention;

[0024] Figure 3 It is a schematic diagram of the energy level structure of the quantum simulator according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0026] In the embodiments of this application, the term "and / or" merely describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist simultaneously, and B exists alone.

[0027] The terms "first" and "second" in the embodiments of this application are only for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of this application, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a system, product, or device that includes a series of components or units is not limited to the listed components or units, but may optionally further include components or units not listed, or may optionally further include other components or units inherent to these products or devices. In the description of this application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0028] Referring to "embodiments" herein means that the specific features, structures, or characteristics described in connection with the embodiments may be included in at least one embodiment of this application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein may be combined with other embodiments.

[0029] In the research of condensed matter physics, although remarkable achievements have been made in many aspects, due to the limitations of experimental systems and research methods, there are still many unsolved problems in the field of strongly correlated many-body systems, such as high-temperature superconductivity, quantum magnets, and quantum phase transitions. By constructing a quantum simulator, these problems can be experimentally studied. During the quantum simulation process, people often focus on some critical phenomena, such as the phase transition point. The quantum simulation process does not require high-fidelity quantum manipulation, thus attracting extensive attention. Universal quantum simulation is achieved by establishing a mapping between the research object and the simulator, and directly simulating the Hamiltonian of the quantum system to be studied using a controllable quantum system. Since the Hamiltonian of the simulation system corresponds to the Hamiltonian of the model to be simulated, one can select an appropriate projection according to the problem to be studied to investigate the dynamic or ground state properties of the system. The most important advantage of universal quantum simulation is that it has relatively low requirements for the manipulation accuracy of the simulator and has a certain fault tolerance ability, being effective even in the presence of errors.

[0030] Therefore, the embodiments of the present invention plan to conduct research on a universal quantum simulator based on a cold atom system, and realize the quantum simulation of specific physical and chemical models by precisely manipulating the microwave field frequency and polarization. By selecting atoms with more hyperfine structure Zeeman magnetic sub-levels, such as cesium atoms, higher-dimensional quantum manipulation and simulation can be achieved. This universal quantum simulator has important scientific significance in both scientific research and industrial applications. The following will be elaborated and introduced through multiple embodiments.

[0031] Figures 1 to 3 A universal quantum simulator based on a cold atom system according to an embodiment of the present invention includes a three-dimensional magneto-optical trap, a glass vacuum chamber 5, an atomic release agent 8, and a photomultiplier tube detector 17;

[0032] The glass vacuum chamber 5 is used to form a closed high-vacuum background environment; the glass vacuum chamber is used to form a closed high-vacuum background environment (Pa), thereby reducing the collision between atoms and background gas and enabling them to have a longer lifespan;

[0033] The atomic release agent 8 is used to release the atoms required by the simulator into the vacuum glass chamber 5; the atomic release agent 8 undergoes a reduction reaction by current heating to release the alkali metal atoms required by the simulator, and uses the hyperfine structure Zeeman magnetic sub-levels of the atoms for quantum simulation;

[0034] The three-dimensional magneto-optical trap is used to construct a quadrupole magnetic field required for trapping atoms, and trap the atoms at the center of the quadrupole magnetic field to form a cold atom cloud; the cold atom cloud is realized by the three-dimensional magneto-optical trap. The magneto-optical trap mainly consists of a pair of anti-Helmholtz coils 6 and three pairs of counter-propagating laser beams 16. The trapping force mainly relies on the scattering force of the laser beams 16. The kinetic energy of the atoms is taken away by photons to cool them. At the same time, the quadrupole magnetic field provides an environment where the radiation pressure varies with position, so that the atoms at the center of the anti-Helmholtz coils 6 are subjected to an optical scattering force that always points to the center, thereby achieving the purpose of trapping and cooling. The combination of the optical field and the magnetic field finally cools and traps a cloud of cold atoms 12 at the center of the quadrupole magnetic field; the laser beams 16 are used for atom trapping and detection, and to provide the pulse sequence required by the quantum simulator;

[0035] Since atoms have a magnetic dipole moment, when in an external magnetic field, the hyperfine structure will split into multiple Zeeman magnetic sub-levels due to the Zeeman effect. The transition frequency range between different hyperfine structures is in the GHz range, belonging to the microwave band, while the transition frequency range between different Zeeman magnetic sub-levels of the same hyperfine structure is in the MHz range, belonging to the radio frequency band; due to the difference in the transition frequencies between different energy levels, any energy level can be manipulated by selecting the frequency;

[0036] The photomultiplier detector 17 is used to detect atomic fluorescence and extract the evolved atomic information.

[0037] Specifically, it also includes a plurality of microwave horns, and the microwave horns are used to radiate microwave pulses to the cold atom cloud. The microwave horns are used to radiate the required microwave field. The microwave pulses with adjustable intensity, frequency and phase are generated by an arbitrary waveform generator. The interaction between the microwave and the atoms realizes any form of coupling between the internal states of the atoms; in this embodiment, as Figure 2 shown in, it includes a first microwave horn 13, a second microwave horn 14 and a third microwave horn 15;

[0038] Specifically, it also includes a fixing frame 9, and the fixing frame 9 is used to fix the glass vacuum chamber 6 and the three-dimensional magneto-optical trap; the vacuum glass chamber 6 is connected to an ion pump 11 through a tee 7 and a bellows 10; the ion pump 11 is used to maintain a high vacuum state in the glass vacuum chamber 6; the gas molecules in the ion pump 11 are efficiently ionized in the electromagnetic field, and the ions bombard the cathode titanium plate under high voltage, sputtering fresh titanium materials, which are deposited on the anode cylinder wall to adsorb inert gas molecules. The bellows 10 is used to connect the vacuum system (glass vacuum chamber) and the ion pump 11 to avoid hard connection

[0039] Specifically, the pressure in the glass vacuum chamber 11 is not greater than 10 -9 Pa.

[0040] Specifically, the three-way joint 7 is connected to a mechanical molecular pump, and the mechanical molecular pump is used to create a primary vacuum environment in the glass vacuum chamber.

[0041] Before performing quantum simulation, the internal state of the cold atoms needs to be prepared into the initial state |1>. Subsequently, through microwave combinations of different frequencies and polarizations (such as Figure 3 shown, σ + is right-handed circular polarization, π is linear polarization, σ - is left-handed circular polarization), the preparation of any initial state is achieved.

[0042] As Figure 3 shown, in the quantum simulator, taking rubidium-87 atoms as an example: there are 3 Zeeman magnetic sub-levels in the hyperfine level F = 1 energy level, which are: |1> = |F = 1, m f = 1>, |2> = |F = 1, m f = 0> and |3> = |F = 1, m f = -1>; there are 5 Zeeman magnetic sub-levels in the hyperfine level F = 2 energy level, which are: |4> = |F = 2, m f = -2>, |5> = |F = 2, m f = -1>, |6> = |F = 2, m f = 0>, |7> = |F = 2, m f = 1> and |7> = |F = 2, m f = 2>. Through 15 microwave beams with different intensities, polarizations and phases, full-connected coupling of 8 energy levels can be achieved, and then quantum simulation of specific physical models within 8 dimensions can be carried out.

[0043] Taking the quantum simulation of Hopfield neurons as an example. As Figure 1 shown, through a one-to-one mapping relationship, the four neurons 1, 2, 3, and 4 in the model are mapped to four specific energy levels among the selected ones: |2> = |F = 1, m f = 0>, |3> = |F = 1, m f = -1>, |5> = |F = 2, m f = -1> and |6> = |F = 2, m f = 0>. The weights (w 12 , w 13 , w 14 , w 24 , w 23 , w 34 ) between different neurons are mapped into the coupling strengths between the corresponding energy levels, and then the quantum simulation of the Hopfield model is realized. By simulating the information transmission between neurons through a controllable quantum system, it provides a possibility for realizing a non von Neumann architecture computing mode.

[0044] In summary, the quantum simulator according to the embodiments of the present invention uses microwave pulses to manipulate atomic clusters. Microwaves have a longer wavelength, which can make the field strength felt by the atoms more uniform. Therefore, the microwave-based control system has a longer coherence time and can perform more operations; it is not limited to using a specific atom and has greater selectivity. Appropriate atoms can be selected for manipulation according to the number of energy levels required by a specific model, and there is a greater flexibility in terms of the difficulty of manipulation; both its control and detection technologies are currently relatively mature technologies. By selecting microwaves with appropriate intensity, frequency, and phase, the manipulation of corresponding energy levels can be achieved. During detection, the ground-state clusters are excited to the excited state, and the relative atomic number of this energy level can be deduced by collecting the fluorescence of spontaneous emission of the excited-state atoms. By combining the method of multiple measurements, the measurement of the atomic number of any energy level can be achieved. The fluorescence normalization detection method has the characteristics of high signal-to-noise ratio and is widely used in cold atom experiments.

[0045] The various embodiments of the present invention can be combined arbitrarily to achieve different technical effects.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A general quantum simulator based on a cold atom system, characterized in that, it includes a three-dimensional magneto-optical trap, a glass vacuum chamber, an atomic release agent, a photomultiplier tube detector, and multiple microwave horns; the glass vacuum chamber is used to form a closed high-vacuum background environment; the atomic release agent is used to release the atoms required by the simulator into the vacuum glass chamber; the three-dimensional magneto-optical trap is used to construct a quadrupole magnetic field required for trapping atoms, and trap the atoms at the center of the quadrupole magnetic field to form a cold atom cloud; the photomultiplier tube detector is used to detect atomic fluorescence to extract the evolved atomic information; the multiple microwave horns are used to radiate microwave pulses to the cold atom cloud; the microwave pulses are generated by an arbitrary waveform generator, and the intensity, frequency, and phase of the microwave pulses are adjustable; the general quantum simulator based on the cold atom system is used to simulate multi-dimensional physical models and chemical models using the cold atom hyperfine Zeeman magnetic sub-level system. According to the mapping relationship between the system and the models, map the physical models and chemical models to specific energy levels of the atoms; by controlling the intensity, frequency, and phase of the microwave signals generated by the arbitrary waveform generator, arbitrary coupling between different Zeeman magnetic sub-levels can be achieved.

2. The general quantum simulator based on the cold atom system according to claim 1, characterized in that, the three-dimensional magneto-optical trap includes a pair of anti-Helmholtz coils and three pairs of counter-propagating laser beams; the anti-Helmholtz coils are used to form a quadrupole magnetic field in the glass vacuum chamber; the three pairs of counter-propagating laser beams are irradiated to the center of the coils of the anti-Helmholtz coils, so that the atoms at the coil center are subjected to an optical scattering force that everywhere points to the coil center, to capture and cool the atoms.

3. The general quantum simulator based on the cold atom system according to claim 1, characterized in that, the atomic release agent is specifically used to perform a reduction reaction and release the alkali metal atoms required by the simulator when heated by an electric current.

4. The general quantum simulator based on the cold atom system according to claim 1, characterized in that, it further includes a fixing frame, and the fixing frame is used to fix the glass vacuum chamber and the three-dimensional magneto-optical trap; the vacuum glass chamber is connected to an ion pump through a tee and a bellows; the ion pump is used to maintain the high-vacuum state of the glass vacuum chamber; the gas molecules in the ion pump are efficiently ionized in an electromagnetic field, and the ions bombard the cathode titanium plate under the action of high voltage, splashing out fresh titanium materials and depositing them on the anode cylinder wall to adsorb inert gas molecules.

5. The general quantum simulator based on the cold atom system according to claim 1, characterized in that, The pressure inside the glass vacuum chamber is not greater than 10 -9 Pa.

6. The general quantum simulator based on the cold atom system according to claim 4, characterized in that, the tee is connected to a mechanical molecular pump, and the mechanical molecular pump is used to create a primary vacuum environment for the glass vacuum chamber.

Images