Optical atomic clock system

Abstract

The present invention provides an optical atomic clock system comprising: an optical pulse generation component adapted to generate a clock interrogation optical pulse; the atomic furnace is used for generating atomic steam; each subsystem is suitable for capturing and preliminarily cooling atoms in the received atom steam to obtain a cold atomic group, and is used for trapping the atoms in the cold atomic group; the subsystem is constructed to allow clock polling pulse light to enter, so that atoms in a ground state interfere with each other under the action of two clock polling light pulses; the processing component is used for obtaining an error signal of the subsystem according to the interference result in any subsystem; a timing controller configured to: cause atoms within the at least one subsystem to be in an illumination phase of the clock interrogation light pulse or in a free evolutionary phase between two illumination of the clock interrogation light pulse; the frequency of the clock interrogation light pulse is corrected according to the respective error signals of the plurality of subsystems.

Description

An optical atomic clock system Technical Field

[0001] This invention relates to the field of cold atom physics, and in particular to an optical atomic clock system. Background Technology

[0002] Optical atomic clocks, due to their superior accuracy in quantum metrology, have become leading candidates for the next generation of time-frequency standards. Advances in laser cooling and trapping, quantum state control, and ultrastable laser technology have enabled atomic clocks to achieve accuracy less than 10-1. -18 The fractional stability and uncertainty of atomic clocks. Atomic clocks have now been widely developed in a variety of neutral atomic and trapped ion systems. Notably, high-precision clock frequency comparisons have been validated in gravitational redshift measurements. Furthermore, new technological research, such as zero-dead-time (ZDT) atomic clocks and entangled atomic clocks, is expected to further push the performance limits of atomic clocks. These breakthroughs provide the foundation for a future redefinition of the SI unit "second" and support a wide range of fundamental physics applications, including testing changes in fundamental physical constants, precisely verifying general relativity, and searching for gravitational waves and dark matter.

[0003] The stability limit of optical atomic clocks is, in principle, constrained by quantum projection noise, and technically by the noise of the optical local oscillator. Quantum projection noise increases with the number of atoms N. Scaling, for optical lattice atomic clocks with N~10³, has a theoretical limit of less than While quantum entanglement may break this limit, the performance of current atomic clocks is generally still limited by their stability due to the Dicke effect—the dead time during quantum state preparation and readout causing local oscillator noise to alias into the atomic detection signal. The level.

[0004] Current methods for suppressing the Dick effect include: first, enhancing the performance of the local oscillator, which requires a significant improvement in the stability of the ultrastable optical cavity; second, employing longitudinal Ramsey spectroscopy in a moving optical lattice, which requires precise stabilization of the laser and magnetic field; and third, using the ZDT method with alternating probes of cold atoms in the optical lattice, which requires two independent cold atom systems. The first method falls under the research scope of ultrastable laser technology. The second and third methods involve the design of cold atom physics systems. The advantage of the second method is that it only requires one atomic system with a two-dimensional moving optical lattice to suppress the Dick effect, but its disadvantage is that the atoms are in continuous motion, thus limiting the accuracy of the atomic clock frequency assessment. The advantage of the third method is that keeping the atoms in a constant optical lattice allows for both high-precision system stability and uncertainty assessment, but its disadvantage is the large system size, which limits the application scenarios of movable atomic clocks. Summary of the Invention

[0005] To address the above problems, the present invention provides an optical atomic clock system.

[0006] This invention provides an optical atomic clock system, comprising:

[0007] Optical pulse generating component, suitable for generating clock interrogation optical pulses;

[0008] Atomic furnaces are used to generate atomic vapor;

[0009] Multiple subsystems, each suitable for trapping and initially cooling atoms in received atomic vapor to obtain cold atomic clusters, and for trapping atoms in cold atomic clusters; each subsystem is configured to allow polarized light to enter and irradiate the trapped atoms within the subsystem, causing the trapped atoms to be in the ground state; each subsystem is also configured to allow clock probing pulses to enter and irradiate the atoms in the ground state, so that the atoms in the ground state interfere under the action of two consecutive clock probing pulses;

[0010] The processing component determines the error between the frequency of the clock probing light pulse and the transition frequency of the atom based on the interference result within any subsystem, thereby obtaining the error signal of the subsystem.

[0011] The timing controller is configured as follows:

[0012] The atoms in at least one subsystem are either in the irradiation phase of a clock probing pulse or in the free evolution phase between two clock probing pulse irradiations.

[0013] Based on the error signals of each of the multiple subsystems, the frequency of the clock probing light pulse is corrected to lock the frequency of the clock probing light pulse to the transition frequency of the atom. The locked clock probing light pulse is used as a timing reference signal.

[0014] According to an embodiment of the present invention, the optical atomic clock system further includes: a beam splitting component, adapted to divide the clock probing light pulse into multiple sub-light pulses, and to transmit the multiple sub-light pulses to multiple subsystems respectively;

[0015] The timing controller is also configured to:

[0016] The light incident on the two subsystems at the same time is the same, so that the atoms in the two subsystems are in the same state;

[0017] The frequency of any sub-optical pulse is corrected based on the error signals of each of the multiple subsystems.

[0018] According to an embodiment of the present invention, the timing controller is further configured to:

[0019] The operating performance of the subsystem is determined based on the error signals of each of the multiple subsystems.

[0020] According to an embodiment of the present invention, the subsystem includes:

[0021] A cooling vacuum chamber has a first accommodating space inside to hold atomic vapor. The cooling vacuum chamber has multiple pairs of facing first windows, which form a first channel, a second channel, and three mutually orthogonal third channels. The first channel is used to allow external Zeeman decelerated light to enter the cooling vacuum chamber, the second channel is used to allow external modulated light to enter the cooling vacuum chamber, and the three third channels are used to allow external cooling light to enter the cooling vacuum chamber.

[0022] A gradient magnetic field structure, located within the cooling vacuum cavity, is suitable for generating a gradient magnetic field. The gradient magnetic field, in conjunction with the Zeeman deceleration light, decelerates the atoms in the atomic vapor. The gradient magnetic field structure is also configured to form a magneto-optical trap in conjunction with the cooling light to capture and Doppler cool the decelerated atoms, resulting in cold atom clusters. The modulated light is suitable for removing the cold atom clusters from the cooling vacuum cavity.

[0023] According to an embodiment of the present invention, the subsystem further includes:

[0024] An optical resonant cavity includes:

[0025] An experimental vacuum chamber has a second accommodating space inside to hold cold atom clusters. Multiple pairs of facing second windows are formed on the experimental vacuum chamber, forming a fourth channel and a fifth channel. The fourth channel and the second channel are collinear and connected. Modulated light is incident into the cooling vacuum chamber from the second channel and the fourth channel in opposite directions to move the cold atom clusters from the cooling vacuum chamber into the experimental vacuum chamber.

[0026] Two opposing reflective components are positioned at both ends of the fifth channel in the experimental vacuum cavity. Lattice light is reflected back and forth between the two reflective components along the fifth channel, forming an optical lattice within the experimental vacuum cavity. The optical lattice is used to trap atoms in cold atom clusters. Two external sideband cooling beams are incident into the experimental vacuum cavity from both ends of the fifth channel to further cool the trapped atoms.

[0027] According to an embodiment of the present invention, the subsystem further includes:

[0028] A vacuum thermal window has a pair of facing third windows formed on it, which form a sixth channel. The sixth channel and the first channel are collinear and connected. The Zeeman decelerating light is incident into the cooling vacuum cavity along the sixth channel and the first channel in sequence.

[0029] According to an embodiment of the present invention, both the cooling vacuum chamber and the experimental vacuum chamber are provided with magnetic shielding structures on their outer peripheries.

[0030] According to an embodiment of the present invention, the processing component includes:

[0031] The detection unit is configured as follows:

[0032] After a coherent quantum leap occurs, the signal is emitted to the trapped atoms to obtain the first fluorescence signal;

[0033] A heavy pump light is emitted to the trapped atoms to return the excited atoms to the ground state;

[0034] A second probe light is emitted towards the trapped atoms to obtain a second fluorescence signal;

[0035] After the trapped atoms have completely disappeared, a third probe light is emitted to obtain a third fluorescence signal;

[0036] The computing unit is configured to calculate the proportion of coherent quantum transitions occurring in the trapped atoms based on the first fluorescence signal, the second fluorescence signal, and the third fluorescence signal, and to determine the error signal based on the proportion.

[0037] According to an embodiment of the present invention, the subsystem further includes:

[0038] A temperature control unit is installed on the experimental vacuum chamber and is used to keep the temperature inside the experimental vacuum chamber constant.

[0039] The experimental vacuum chamber is also equipped with a bias magnetic field assembly, which is suitable for generating a static magnetic field. The static magnetic field works in conjunction with the polarization light to initialize the quantum state of the trapped atoms.

[0040] According to an embodiment of the present invention, the gradient magnetic field and the Zeeman deceleration light work together to reduce the velocity of atoms in the atomic vapor input into the cooling vacuum cavity to below 50 m / s.

[0041] According to embodiments of the present invention, multiple (at least two) subsystems are scheduled to operate alternately by a timing controller, ensuring that atoms in at least one subsystem are either in the irradiation phase of a clock probing light pulse or in a free evolution phase between two clock probing light pulse irradiations. This eliminates the dead time in the quantum state preparation and readout process of traditional optical clocks, resulting in higher stability of the atomic clock and providing a core guarantee for high-precision time and frequency measurement. The atomic furnace in this embodiment simultaneously supplies atomic vapor to multiple subsystems, eliminating the need for a separate atomic source for each subsystem. This reduces redundant components, avoids the volume redundancy caused by the traditional dual-system distributed layout, and makes the overall structure smaller, easier to integrate, and more portable for deployment. Attached Figure Description

[0042] The above and other objects, features and advantages of the present invention will become more apparent from the following description of the invention with reference to the accompanying drawings, in which:

[0043] Figure 1 shows a schematic diagram of an optical atomic clock system provided according to an embodiment of the present invention.

[0044] Figure 2 shows a schematic diagram of the ZDT operating mode of the optical atomic clock system provided according to an embodiment of the present invention.

[0045] Explanation of reference numerals in the attached figures:

[0046] 1. Atomic furnace; 2. Subsystem; 21. Cooling vacuum chamber; 211. First window; 211a. First channel; 211b. Second channel; 211c. Third channel; 22. Optical resonant cavity; 221. Experimental vacuum chamber; 222. Reflection assembly; 2211. Second window; 2211a. Fourth channel; 2211b. Fifth channel; 23. Vacuum thermal window; 231. Third window; 231a. Sixth channel; 223. Bias magnetic field assembly; 24. Magnetic shielding structure; 25. Gradient magnetic field structure. Detailed Implementation

[0047] In the process of realizing this invention, it was discovered that a dead-time-free atomic clock system with two cold atom optical lattices can be developed. This system combines moving optical lattice technology and dual independent atom physics technology, which can not only suppress the Dick effect of atomic clocks and realize ZDT atomic clock operation with higher frequency stability, but also achieve independent operation without interference, ensuring higher frequency accuracy of ZDT atomic clocks. In addition, it has the characteristics of miniaturization, integration and anti-interference, realizing the portability of high-performance atomic clocks and expanding the experimental application scenarios of high-precision atomic clocks.

[0048] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0049] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0050] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0051] Figure 1 shows a schematic diagram of an optical atomic clock system provided according to an embodiment of the present invention.

[0052] As shown in Figure 1, the optical atomic clock system includes: an atomic furnace 1, multiple subsystems 2, a processing component, a light pulse generation component, and a timing controller. In this embodiment of the invention, "multiple" refers to at least two subsystems; Figure 1 illustrates an optical atomic clock system comprising two subsystems as an example.

[0053] A light pulse generation component is used to generate clock probing light pulses. An atomic furnace 1 is used to store solid atoms (such as strontium and ytterbium) and has a high-temperature heating function, reaching temperatures up to 700°C, to generate atomic vapor. Each subsystem 2 is used to capture and initially cool atoms in the received atomic vapor to obtain cold atomic clusters, and to trap atoms within the cold atomic clusters. Subsystem 2 is configured to allow polarized light to enter and irradiate the trapped atoms, causing quantum state initialization of the trapped atoms in any subsystem 2, placing them in the ground state. Subsystem 2 is also configured to allow clock probing light pulses to enter and irradiate the atoms in the ground state, causing interference between the atoms in the ground state under the influence of two consecutive clock probing light pulses (for strontium atoms, a 698nm clock probing light pulse can be used). A processing component determines the error between the frequency of the clock probing light pulse and the transition frequency of the atoms based on the interference result within any subsystem 2, obtaining the subsystem's error signal. A timing controller is configured to: place atoms in at least one subsystem in an illumination phase of a clock probe light pulse or in a free evolution phase between two clock probe light pulse illuminations; and, based on error signals from multiple (e.g., two) subsystems, correct the frequency of the clock probe light pulses to lock the frequency of the clock probe light pulses at the transition frequency of the atoms, wherein the locked clock probe light pulses are used as timing reference signals.

[0054] According to embodiments of the present invention, multiple (e.g., two) subsystems are scheduled to operate alternately by a timing controller, ensuring that atoms in at least one subsystem are either in the irradiation phase of a clock probing light pulse or in a free evolution phase between two clock probing light pulse irradiations. This eliminates the dead time in the quantum state preparation and readout process of traditional optical clocks, resulting in higher stability of the atomic clock and providing a core guarantee for high-precision time and frequency measurement. The atomic furnace in this embodiment simultaneously supplies atomic vapor to multiple subsystems, eliminating the need for a separate atomic source for each subsystem. This reduces redundant components, avoids the volume redundancy caused by the traditional dual-system distributed layout, and makes the overall structure smaller, easier to integrate, and more portable for deployment.

[0055] According to an embodiment of the present invention, the optical atomic clock system further includes: a beam splitting component adapted to divide the clock probing light pulse into multiple sub-light pulses and transmit the multiple sub-light pulses to multiple subsystems respectively.

[0056] The timing controller is also configured to ensure that the light incident on the two subsystems at the same time is identical, so that the atoms in the two subsystems are in the same state. The frequency of any sub-light pulse is corrected based on the error signals of each of the multiple subsystems.

[0057] According to an embodiment of the present invention, the timing controller is further configured to determine the operating performance of a subsystem based on the error signals of each of the multiple subsystems.

[0058] According to an embodiment of the present invention, subsystem 2 includes a cooling vacuum cavity 21 and a gradient magnetic field structure 25. The cooling vacuum cavity 21 may be, for example, a regular octagonal cavity (made of stainless steel or titanium alloy). Multiple pairs of facing first windows 211 are formed on the cooling vacuum cavity 21, and the first windows 211 are coated with quartz or sapphire. The multiple pairs of first windows form a first channel 211a, a second channel 211b, and three mutually orthogonal third channels 211c. The first channel 211a is used to allow external Zeeman decelerated light to enter the cooling vacuum cavity 21; the second channel 211b is used to allow external modulated light to enter the cooling vacuum cavity 21; and the third channel 211c is used to allow external cooling light to enter the cooling vacuum cavity 21. A gradient magnetic field structure 25, located within the cooling vacuum cavity 21, is used to generate a gradient magnetic field. This gradient magnetic field, in conjunction with Zeeman deceleration light, decelerates atoms in the atomic vapor input into the cooling vacuum cavity 21. The gradient magnetic field structure is also configured to form a magneto-optical trap in conjunction with the cooling light to capture and Doppler-cool the decelerated atoms, resulting in cold atom clusters. The modulated light is used to remove the cold atom clusters from the cooling vacuum cavity.

[0059] According to an embodiment of the present invention, there are two Zeeman-depressed beams, incident in opposite directions from two opposing first windows 211 forming the first channel 211a. The Zeeman-depressed beams have a specific frequency detuning; for example, for strontium atoms, a 461 nm Zeeman cooling beam is used. There are three pairs of cooling beams, each pair consisting of three mutually orthogonal beams. The laser consists of polarized configurations, with each pair of cooling beams incident in opposite directions from two opposing first windows 211 of the corresponding third channel 211c. Schematic, for strontium atoms, a 461nm first-order cooling beam can achieve atomic temperatures in the mK range, and a 689nm second-order cooling beam can achieve atomic temperatures in the μK range.

[0060] According to an embodiment of the present invention, the gradient magnetic field generated by the gradient magnetic field structure 25, in conjunction with the Zeeman deceleration light incident through the first channel 211a, can decelerate the atomic vapor input into the cooling vacuum cavity 21 to below 50 m / s. Simultaneously, the gradient magnetic field structure 25, together with the cooling light incident through three mutually orthogonal third channels 211, forms a magneto-optical trap, which can precisely capture and Doppler cool the decelerated atoms, stably obtaining cold atom clusters on the mK or even μK scale, laying the foundation for subsequent atomic manipulation.

[0061] According to an embodiment of the present invention, subsystem 2 further includes an optical resonant cavity 22. The optical resonant cavity 22 includes an experimental vacuum cavity 221 and two opposing reflective components 222. The experimental vacuum cavity 221 has a regular cubic cavity structure (made of stainless steel or titanium alloy). Multiple pairs of facing second windows 2211 are formed on the experimental vacuum cavity 221, and the second windows 2211 are coated with quartz or sapphire. The multiple pairs of facing second windows 2211 form a fourth channel 2211a and a fifth channel 2211b, wherein the fourth channel 2211b and the second channel are collinear and connected. Two modulated beams (for strontium atoms, 813 nm modulated beams can be used) are incident into the cooling vacuum cavity from the third channel and the fourth channel, respectively, in opposite directions. One modulated beam is incident from a first window forming the second channel and located away from the optical resonant cavity, and the other modulated beam is incident from a second window forming the fourth channel and located away from the cooling vacuum cavity.

[0062] Two opposing reflective components 222 are positioned at both ends of the fifth channel 2211b in the experimental vacuum cavity 221. The reflective components 222 are composed of high reflectivity mirrors. The lattice light is reflected back and forth between the two reflective components along the fifth channel, and the cyclic gain coefficient between the two reflective components 222 is greater than 50. The lattice light forms an optical lattice in the experimental vacuum cavity to trap atoms in the cold atom cluster. The fifth channel is used to allow external sideband cooling light to enter the experimental vacuum cavity. There are two external sideband cooling lights, which are incident in opposite directions to further cool the trapped atoms.

[0063] According to an embodiment of the present invention, the frequency of the lattice light resonates with the optical resonant cavity. For example, for strontium atoms, an 813nm laser is used as the lattice light, and a 689nm laser is used as the sideband cooling light.

[0064] According to an embodiment of the present invention, differential tubes (vacuum differential ratio greater than 10 times) are provided in both the experimental vacuum cavity and the optical resonant cavity. Each subsystem includes a vacuum pump. The differential tubes and the vacuum pump work together to maintain the interior of the vacuum cavity 21 and the interior of the experimental vacuum cavity as a vacuum.

[0065] According to an embodiment of the present invention, the fourth channel 2211a of the experimental vacuum cavity 221 is collinear with and connected to the second channel of the cooling vacuum cavity. Modulated light can be incident relative to each other along the two channels, efficiently and accurately transferring the cold atom clusters prepared in the cooling vacuum cavity to the central region of the experimental vacuum cavity 221. Simultaneously, two opposing reflection components 222 arranged at both ends of the fifth channel 2211b cause lattice light to reflect back and forth between them, forming a stable optical lattice within the experimental vacuum cavity 221. This reliably traps the transferred cold atom clusters, preventing atomic escape and providing a stable atomic sample for subsequent quantum state manipulation and clock probing processes. The fourth channel 2211a and the fifth channel 2211b formed by multiple pairs of second windows 2211 on the experimental vacuum cavity 221 achieve independent incident and transmission of modulated light and lattice light, avoiding crosstalk interference between different optical fields.

[0066] According to an embodiment of the present invention, each subsystem further includes a vacuum thermal window 23. A pair of facing third windows 231 are formed on the vacuum thermal window 23, and the facing third windows form a sixth channel 231a. The sixth channel 231a and the first channel 211a are collinear and connected. The Zeeman decelerating light is incident into the cooling vacuum chamber 21 in sequence along the sixth channel and the first channel 211a.

[0067] According to an embodiment of the present invention, the sixth channel 231a of the vacuum hot window 23 is collinear with and connected to the first channel of the cooling vacuum cavity 21, so that the Zeeman decelerating light can pass through the sixth channel 231a and the first channel sequentially along a preset path and point to the center of the cooling vacuum cavity 21, avoiding the decrease in deceleration efficiency caused by the optical field transmission offset, and ensuring that the high-speed atomic vapor is stably decelerated to below 50m / s under the cooperation of the gradient magnetic field, providing a reliable premise for the preparation of cold atomic clusters.

[0068] According to an embodiment of the present invention, the temperature of the sapphire lens inside the vacuum hot window 23 can reach 350°C, thus it has a high-temperature heating function, which can effectively prevent atomic vapor from condensing and contaminating on the surface of the third window 231, avoiding Zeeman deceleration light transmission loss or optical path distortion caused by window contamination; at the same time, its connection design with the cooling vacuum cavity 21 further enhances the vacuum sealing of the entire atomic transmission link, reduces the interference of vacuum environment damage on the atomic deceleration and capture process, and improves the stability of subsystem operation.

[0069] According to an embodiment of the present invention, a bias magnetic field component 223 is also provided inside the experimental vacuum cavity. The bias magnetic field component 223 is suitable for generating a static magnetic field. The static magnetic field, in conjunction with polarized light, enables the trapped atoms to undergo quantum state initialization.

[0070] According to an embodiment of the present invention, the bias magnetic field component 223 (bias coil or ring permanent magnet) generates a stable static magnetic field in the experimental vacuum cavity. The polarization light, in synergy, uniformly polarizes the cold atoms trapped in the optical lattice to their ground state, achieving quantum state initialization. This process effectively eliminates interference from stray quantum states, ensuring that atoms undergo only coherent transitions between the ground and excited states during the subsequent clock probing stage (clock probing light pulse action). This improves the purity and detectability of the transition signal, providing a core guarantee for the accuracy of the optical clock frequency.

[0071] According to an embodiment of the present invention, a magnetic shielding structure 24 is provided on the outer periphery of both the cooling vacuum cavity and the experimental vacuum cavity. The magnetic shielding structure is composed of permalloy material that has undergone thermal annealing, and has a suppression ratio of more than 20 for ambient magnetic field signals (frequency 50Hz and below). The magnetic shielding structure 24 surrounds the outer periphery of the cooling vacuum cavity and the experimental vacuum cavity, which can effectively prevent the gradient magnetic field generated by the gradient magnetic field structure inside the cooling vacuum cavity from interfering with the bias magnetic field generated by the bias magnetic field structure inside the experimental vacuum cavity. This avoids the magnetic field distribution distortion caused by the superposition of the two magnetic fields, and ensures that the deceleration effect of the gradient magnetic field on atomic vapor, the atomic trapping and cooling function of the magneto-optical trap, and the supporting effect of the bias magnetic field on the preparation of quantum state polarization of cold atoms in the optical lattice are not interfered with, thus ensuring the progress of each step such as atomic cooling, transfer, and quantum state initialization.

[0072] According to an embodiment of the present invention, the processing component includes a detection unit and a computing unit. The detection unit is configured to: after a coherent quantum transition occurs, emit a first detection light to the trapped atom to obtain a first fluorescence signal; emit a repump light to the trapped atom to return the excited atom to the ground state; emit a second detection light to the trapped atom to obtain a second fluorescence signal; and emit a third detection light to obtain a third fluorescence signal after the trapped atom has completely disappeared. The computing unit is used to calculate the proportion of coherent quantum transitions occurring in the trapped atom based on the first, second, and third fluorescence signals, and to determine an error signal based on the proportion. For strontium atoms, the wavelengths of the first, second, and third detection lights are 461 nm, and the wavelength of the repump light is 707 nm.

[0073] According to an embodiment of the present invention, the subsystem further includes a temperature control unit. This temperature control unit includes a temperature detector (such as a PT100 platinum resistance thermometer) and a water-cooling loop. The temperature control unit is disposed on the experimental vacuum chamber and is suitable for maintaining a constant temperature inside the experimental vacuum chamber.

[0074] The temperature control unit maintains a constant temperature inside the experimental vacuum cavity, avoiding deformation of the cavity, drift of the optical resonant cavity length, and distortion of the optical lattice potential well structure caused by temperature fluctuations. This ensures the stability of the energy level structure of cold atoms in the optical lattice, reduces temperature-related blackbody radiation frequency shift fluctuations, keeps the energy level difference between the atomic ground state and excited state constant, and thus ensures the resonance matching accuracy between the clock probing light pulse and the atomic energy level, as well as the frequency accuracy of the atomic clock.

[0075] Referring to Figure 1 and specific embodiments, the operation of the optical atomic clock system will be described below.

[0076] In atomic furnace 1, room-temperature solid atoms are heated to high temperature and transformed into atomic vapor, which then enters cooling vacuum chamber 21. The gradient magnetic field structure within cooling vacuum chamber 21 generates the gradient magnetic field required for atomic cooling. This gradient magnetic field along the direction of atomic motion allows the high-speed atomic vapor to be continuously decelerated to below 50 m / s under the influence of Zeeman decelerating light. At the center of the cooling vacuum chamber, a three-dimensional gradient magnetic field and three pairs of atomic cooling lights (each pair forming...) create... (Polarization configuration) forms a magneto-optical trap to capture and Doppler cool atoms after continuous deceleration, achieving cold atom clusters with temperatures on the order of mK or even μK.

[0077] Two opposing modulated light fields of the combined modulation light are activated, transferring the cold atom cluster in the cooling vacuum cavity 21 into the experimental vacuum cavity 221. Once the cold atom cluster is completely transferred to the center of the experimental vacuum cavity 221, the lattice light field is activated, allowing lattice light to enter the experimental vacuum cavity 221 to load the cold atoms, while the modulation light is deactivated. The lattice light field forms a one-dimensional cavity-enhanced optical lattice in the optical resonant cavity 22. The bias magnetic field assembly 223 within the experimental vacuum cavity 221 generates the bias magnetic field required for the atomic experiment, activating the polarization light field and allowing polarized light (689 nm for strontium atoms) to enter the experimental vacuum cavity 221, thus using the polarized light to prepare the quantum state of the optically lattice-trapped cold atoms through quantum polarization. The polarization light field is deactivated, and the sideband cooling light field is activated, allowing cooling light to enter the experimental vacuum cavity 221 to further reduce the temperature of the optically lattice-trapped cold atoms to below 1 μK. The sideband cooling light field is turned off, and the clock probing light field is turned on, allowing the clock probing light pulse to be incident into the experimental vacuum cavity 221 to perform Rabi or Ramsey probing on the optical lattice cold atoms, causing the atoms to transition from the ground state to the excited state. The clock probing light field is turned off, and the probe light field is turned on, causing the first probe light to excite the number of ground-state atoms to emit a first fluorescence signal. The first fluorescence signal is used to characterize the number of ground-state atoms. The first probe light field is turned off, and the re-pump light field is turned on to pump the excited-state atoms to the ground state using the re-pump light. The probe light field is then turned on again to excite the ground-state atoms to emit a second fluorescence signal using the second probe light. This second fluorescence signal is used to characterize the number of excited-state atoms. Record the noise floor when the atoms completely disappear. Therefore, the activation ratio corresponding to Zhong Yueqian's inquiry this time is... The two subsystems (e.g., subsystem a and subsystem b) can operate independently and / or collaboratively. In independent operation, a single subsystem undergoes the aforementioned stages of atomic cooling, atomic transfer, atomic polarization, clock probing and atomic evolution, and atomic detection. Ultimately, based on the excitation proportional feedback clock of atomic detection, it searches for the optical frequency, achieving closed-loop operation of the atomic clock system. In collaborative operation, the two subsystems can achieve high-precision time synchronization, enabling ZDT operating mode, dual-clock synchronous comparison mode, and dual-clock asynchronous comparison mode.

[0078] In ZDT operating mode, subsystem a and subsystem b operate alternately.

[0079] While subsystem a is in the atomic cooling, transfer, polarization, and detection stages (i.e., the irradiation stages of Zeeman slowing light, cooling light, modulation light, polarization light, lattice light, first detector light, re-pump light, second detector light, and third detector light), subsystem b is in the atomic free evolution stage. When atoms in subsystem a are irradiated by a preceding clock-probing light pulse, atoms in subsystem b are irradiated by a subsequent clock-probing light pulse. When atoms in system a are in the free evolution stage, atoms in system b are in the cooling, transfer, polarization, and detection stages. When atoms in system a are irradiated by a subsequent clock-probing light pulse, atoms in system b are irradiated by a preceding clock-probing light pulse. Through clock-probing light pulses (frequency... The polling operation on the optical lattice atoms of subsystems a and b realizes a clock probing strategy without dead time.

[0080] Figure 2 shows a schematic diagram of the ZDT operating mode of the optical atomic clock system provided according to an embodiment of the present invention.

[0081] In Figure 2, the Atom region represents the atomic cooling, transfer, polarization, and detection stages; the Ramsey region represents the atomic free evolution stage; and the region between the Atom and Ramsey regions represents the clock probing pulse irradiation stage.

[0082] As shown in Figure 2, the frequency detuning of the clock probing light sensed by the cold atom system within the optical lattice of the two subsystems. and The frequency of the clock probe light pulse is corrected to obtain a new frequency for the clock probe light pulse. . This enables the operation of a timeless optical clock and suppresses the Dick effect.

[0083] In the dual-clock synchronization comparison mode, subsystem a and subsystem b are completely synchronized. At this time, the dual-clock frequency comparison of subsystem a and subsystem b is performed by... The measurement results also eliminate the Dick effect, which can be used to suppress common-mode noise. In the dual-clock asynchronous comparison mode, the operating sequence of subsystems a and b is consistent with the ZDT operating mode, but they are not used for joint feedback to the clock probing light pulses. It can be characterized as the operating performance of a single system.

[0084] The dead-time-free optical clock system with two cold atom optical lattices provided in this invention combines moving optical lattice technology and dual independent atom physics technology. It can not only suppress the Dick effect of the optical clock and realize the operation of the ZDT optical clock, thus achieving higher frequency stability, but also realize independent operation without interference, ensuring higher frequency accuracy of the ZDT optical clock. In addition, it realizes the miniaturization, integration and anti-interference of the optical clock system, realizes the portability of high-performance optical clocks, and greatly expands the experimental application scenarios of high-precision optical clocks.

Claims

1. An optical atomic clock system, comprising: Optical pulse generating component, suitable for generating clock interrogation optical pulses; Atomic furnaces are used to generate atomic vapor; Multiple subsystems, each suitable for trapping and initially cooling atoms in received atomic vapor to obtain cold atomic clusters, and for trapping atoms in cold atomic clusters; each subsystem is configured to allow polarized light to enter and irradiate the trapped atoms within the subsystem, causing the trapped atoms to be in the ground state; each subsystem is also configured to allow clock probing pulses to enter and irradiate the atoms in the ground state, causing the atoms in the ground state to interfere under the action of two consecutive clock probing pulses; a processing component, based on the interference result within any subsystem, determines the error between the frequency of the clock probing pulse and the transition frequency of the atoms, obtaining the error signal of the subsystem; A timing controller is configured to: place atoms in at least one subsystem into an illumination phase of a clock probe light pulse or into a free evolution phase between two clock probe light pulse illuminations; and, based on error signals from multiple subsystems, correct the frequency of the clock probe light pulse to lock the frequency of the clock probe light pulse to the transition frequency of the atom, wherein the locked clock probe light pulse is used as a timing reference signal.

2. The optical atomic clock system according to claim 1, wherein, The optical atomic clock system further includes: a beam splitter, adapted to divide the clock probing light pulse into multiple sub-light pulses and transmit the multiple sub-light pulses to multiple subsystems respectively; the timing controller is further configured to: make the light incident on the two subsystems at the same time the same, so that the atoms in the two subsystems are in the same state; and correct the frequency of any sub-light pulse according to the error signals of the multiple subsystems respectively.

3. The optical atomic clock system according to claim 1, wherein, The timing controller is further configured to determine the operating performance of the subsystems based on the error signals of the respective subsystems.

4. The optical atomic clock system according to claim 1, wherein, The subsystem includes: a cooling vacuum cavity, which forms a first accommodating space for containing atomic vapor. Multiple pairs of facing first windows are formed on the cooling vacuum cavity, forming a first channel, a second channel, and three mutually orthogonal third channels. The first channel allows external Zeeman decelerating light to enter the cooling vacuum cavity, and the second channel allows external modulated light to enter the cooling vacuum cavity. The three third channels allow external cooling light to enter the cooling vacuum cavity. A gradient magnetic field structure is located within the cooling vacuum cavity and is adapted to generate a gradient magnetic field. The gradient magnetic field, in conjunction with the Zeeman decelerating light, decelerates the atoms in the atomic vapor. The gradient magnetic field structure is also configured to cooperate with the cooling light to form a magneto-optical trap for capturing and Doppler cooling the decelerated atoms, resulting in cold atom clusters. The modulated light is adapted to remove the cold atom clusters from the cooling vacuum cavity.

5. The optical atomic clock system according to claim 4, wherein, The subsystem further includes: an optical resonant cavity, comprising: an experimental vacuum cavity, inside which a second accommodating space for accommodating cold atom clusters is formed; multiple pairs of facing second windows are formed on the experimental vacuum cavity, forming a fourth channel and a fifth channel; the fourth channel and the second channel are collinear and connected; wherein modulated light is incident from the second channel and the fourth channel in opposite directions into the cooling vacuum cavity to move the cold atom clusters from the cooling vacuum cavity into the experimental vacuum cavity; two opposing reflective components are disposed at both ends of the fifth channel in the experimental vacuum cavity; wherein lattice light is reflected back and forth between the two reflective components along the fifth channel and forms an optical lattice in the experimental vacuum cavity; the optical lattice is used to trap atoms in the cold atom clusters; and two external sideband cooling beams are incident from both ends of the fifth channel into the experimental vacuum cavity to further cool the trapped atoms.

6. The optical atomic clock system according to claim 4, wherein, The subsystem further includes: a vacuum thermal window, on which a pair of opposing third windows are formed, the opposing third windows forming a sixth channel, the sixth channel being collinear with and connected to the first channel, and the Zeeman decelerating light sequentially entering the cooling vacuum cavity along the sixth channel and the first channel.

7. The optical atomic clock system according to claim 5, wherein, Both the cooling vacuum chamber and the experimental vacuum chamber are provided with magnetic shielding structures on their outer periphery.

8. The optical atomic clock system according to claim 5, wherein, The processing component includes: a detection unit configured to: after a coherent quantum transition occurs, emit light to the trapped atom to obtain a first fluorescence signal; emit repump light to the trapped atom to return the excited atom to the ground state; emit a second detection light to the trapped atom to obtain a second fluorescence signal; and emit a third detection light to obtain a third fluorescence signal after the trapped atom has completely disappeared; and a calculation unit configured to calculate the proportion of the coherent quantum transition occurring in the trapped atom based on the first fluorescence signal, the second fluorescence signal, and the third fluorescence signal, and determine the error signal based on the proportion.

9. The optical atomic clock system according to claim 5, wherein, The subsystem further includes: a temperature control unit, disposed on the experimental vacuum chamber, suitable for maintaining a constant temperature inside the experimental vacuum chamber; and a bias magnetic field assembly disposed inside the experimental vacuum chamber, the bias magnetic field assembly being suitable for generating a static magnetic field, the static magnetic field cooperating with the polarization light to induce quantum state initialization of the trapped atoms.

10. The optical atomic clock system according to claim 4, wherein, The gradient magnetic field and the Zeeman deceleration light work together to reduce the velocity of atoms in the atomic vapor input into the cooling vacuum chamber to below 50 m / s.

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