CN117852658A - Quantum chip testing method and quantum computer - Google Patents
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Abstract
The invention discloses a testing method of a quantum chip and a quantum computer, the core idea is to construct a virtual quantum bit, firstly, based on a quantum state modulation line of a first selected quantum bit, a quantum state modulation line of a second selected quantum bit, a reading cavity of the second selected quantum bit and an adjustable coupler, the virtual quantum bit is constructed, and the first selected quantum bit and the second selected quantum bit are any two quantum bits in a plurality of adjacent quantum bits. And then, first crosstalk of the quantum bit to be measured on the virtual quantum bit is acquired, wherein the quantum bit to be measured is any one quantum bit of a plurality of adjacent quantum bits or a plurality of non-adjacent quantum bits. And finally, acquiring second crosstalk of the quantum bit to be detected to the adjustable coupler based on the first crosstalk. The scheme for constructing the virtual quantum bit can effectively test the influence of adjacent and non-adjacent quantum bits on the crosstalk of the adjustable coupler, and fills the blank of the prior art.
Description
Technical Field
The invention relates to the technical field of quantum computing, in particular to a testing method of a quantum chip and a quantum computer.
Background
Quantum computation and quantum information are a cross subject for realizing computation and information processing tasks based on the principle of quantum mechanics, and have very close connection with subjects such as quantum physics, computer science, informatics and the like. There has been a rapid development in the last two decades. Quantum computer-based quantum algorithms in factorization, unstructured search, etc. scenarios exhibit far beyond the performance of existing classical computer-based algorithms, and this direction is expected to be beyond the existing computing power. Since quantum computing has a potential to solve specific problems far beyond the development of classical computer performance, in order to realize a quantum computer, it is necessary to obtain a quantum chip containing a sufficient number and a sufficient mass of qubits, and to enable quantum logic gate operation and reading of the qubits with extremely high fidelity. The quantum chip is the core component of the quantum computer, and the quantum chip is the processor for executing quantum computation. Before each quantum chip is formally used on line, all relevant parameters of quantum bits in the quantum chip need to be tested and characterized.
In a qubit expansion architecture based on an adjustable coupler, coupling between two qubits can be achieved through a fixed capacitive coupling and an adjustable coupler capable of adjusting a coupling coefficient, and the adjustable coupler is similar to the structure of the qubit in structure, except that the adjustable coupler does not have a quantum state control line and a resonant cavity capable of directly reading information. When an AC signal is applied to a frequency control line of a certain qubit in a superconducting quantum chip, the frequency of the nearby qubit is changed in addition to the influence of the frequency of the qubit, and this phenomenon is called AC crosstalk. The applicant found that in practical applications, this AC crosstalk effect also exists between the tunable coupler and the qubit, and if the effect is ignored, serious errors and even erroneous results occur in the final result of quantum computation using the superconducting quantum chip.
Therefore, it is a need in the art to provide a solution that can test AC crosstalk between an adjustable coupler and a qubit.
It should be noted that the information disclosed in the background section of the present application is only for enhancement of understanding of the general background of the present application and should not be taken as an admission or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
Disclosure of Invention
The invention aims to provide a testing method of a quantum chip and a quantum computer, which are used for solving the problem that a scheme for testing AC crosstalk between an adjustable coupler and quantum bits is lacking in the prior art.
In order to solve the above technical problems, the present invention provides a method for testing a quantum chip, the quantum chip including an adjustable coupler, a plurality of adjacent qubits having a direct coupling connection relationship with the adjustable coupler, and a plurality of non-adjacent qubits not having a direct coupling relationship, the method comprising:
constructing a virtual qubit based on a quantum state modulation line of a first selected qubit, a quantum state modulation line of a second selected qubit, a reading cavity of the second selected qubit and the adjustable coupler, wherein the first selected qubit and the second selected qubit are any two qubits in the plurality of adjacent qubits;
acquiring first crosstalk of a quantum bit to be detected on the virtual quantum bit, wherein the quantum bit to be detected is any one quantum bit of the adjacent quantum bits or the non-adjacent quantum bits;
and acquiring second crosstalk of the quantum bit to be detected to the adjustable coupler based on the first crosstalk.
Optionally, the obtaining the first crosstalk of the qubit to be measured to the virtual qubit includes:
when a second AC signal is in different values, a plurality of AC modulation spectrums corresponding to the virtual quantum bits are obtained, wherein the second AC signal is a signal applied to a frequency modulation line of the quantum bits to be detected;
and acquiring the first crosstalk based on the acquired plurality of AC modulation spectrums.
Optionally, the AC modulation spectrum of the virtual qubit is obtained by:
the method further includes adjusting a size of a first AC signal to obtain an AC modulation spectrum of the virtual qubit, the first AC signal being a signal applied on a frequency modulation line of the tunable coupler.
Optionally, the adjusting the size of the first AC signal to obtain the AC modulation spectrum of the virtual qubit includes:
performing a Ramsey experiment on the virtual qubit, applying the first AC signal to a frequency modulation line of the tunable coupler between two pi/2 gates of the Ramsey experiment, and applying the second AC signal to a frequency modulation line of the qubit to be tested so as to cause the qubit to be tested to have a crosstalk effect on the virtual qubit, wherein the two pi/2 gates of the Ramsey experiment are applied to a quantum state modulation line of the first selected qubit;
applying a pulse signal for changing a quantum state to the quantum state modulation line of the second selected qubit;
acquiring the bit frequency corresponding to the virtual quantum bit when the first AC signal is based on a Ramsey experiment result;
when the first AC signal is not traversed in a preset range, adjusting the size of the first AC signal, and returning to execute the Ramsey experiment on the virtual quantum bit;
and acquiring the AC modulation spectrum of the virtual quantum bit based on the acquired first AC signal and the corresponding bit frequency, wherein the AC modulation spectrum of the virtual quantum bit is the AC modulation spectrum of the adjustable coupler.
Optionally, the acquiring the first crosstalk based on the acquired plurality of AC modulation spectrums includes:
acquiring a first crosstalk coefficient based on the acquired plurality of AC modulation spectrums, wherein the first crosstalk coefficient reflects the change condition of the AC modulation spectrums along with the second AC signal;
the first crosstalk coefficient is the first crosstalk.
Optionally, the acquiring, based on the acquired plurality of AC modulation spectrums, a first crosstalk coefficient includes:
acquiring a physical model of an AC modulation spectrum of the virtual qubit, wherein the physical model is used for reflecting the expected situation that the bit frequency of the virtual qubit changes along with the first AC signal;
fitting the acquired AC modulation spectrums based on the physical model;
and acquiring the first crosstalk coefficient based on the fitting processing result.
Optionally, the physical model is:
wherein Φ=pi M (x-offset);
x is the value of the first AC signal, y is the bit frequency of the virtual qubit, A, M, d and offset are parameters of the physical model, and α is the non-harmonic parameter value of the virtual qubit.
Optionally, the fitting processing on the acquired AC modulation spectrums based on the physical model includes:
fitting each AC modulation spectrum by using the physical model;
acquiring the value of the offset corresponding to each AC modulation spectrum after fitting;
and acquiring the relation between each second AC signal and the value of the corresponding offset as a first relation.
Optionally, the acquiring the relationship between each of the second AC signals and the value of the corresponding offset is a first relationship, including:
and fitting a relation of the offset along with the change of the second AC signal into a coordinate system of which the abscissa and the ordinate are the second AC signal and the offset respectively, wherein the relation is a first relation.
Optionally, the obtaining the first crosstalk coefficient based on a result of the fitting process includes:
the first crosstalk coefficient is obtained based on the first relationship.
Based on the same inventive concept, the invention also provides a testing device of a quantum chip, the quantum chip comprises an adjustable coupler, a plurality of adjacent quantum bits with direct coupling connection relation with the adjustable coupler and a plurality of non-adjacent quantum bits without direct coupling relation, the testing method comprises the following steps:
a virtual qubit construction module configured to construct a virtual qubit based on a quantum state modulation line of a first selected qubit, a quantum state modulation line of the second selected qubit, a reading cavity of the second selected qubit, and the tunable coupler, the first selected qubit and the second selected qubit being any two qubits of the number of adjacent qubits;
a first crosstalk acquisition module configured to acquire a first crosstalk of a quantum bit to be measured to the virtual quantum bit, the quantum bit to be measured being any one of the plurality of adjacent quantum bits or the plurality of non-adjacent quantum bits;
and the second crosstalk acquisition module is configured to acquire second crosstalk of the quantum bit to be measured to the tunable coupler based on the first crosstalk.
Based on the same inventive concept, the invention also provides a quantum control system, which tests the quantum chip by using the testing method of the quantum chip described in any one of the above feature descriptions, or comprises the testing device of the quantum chip described in the above feature descriptions.
Based on the same inventive concept, the invention also provides a quantum computer, which comprises the quantum control system described in the above characteristic description.
Based on the same inventive concept, the invention further provides a readable storage medium, on which a computer program is stored, which when being executed by a processor, can implement the method for testing the quantum chip according to any one of the above feature descriptions.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a testing method of a quantum chip, which is characterized in that a virtual quantum bit is constructed, and the virtual quantum bit is constructed firstly based on a quantum state modulation line of a first selected quantum bit, a quantum state modulation line of a second selected quantum bit, a reading cavity of the second selected quantum bit and the adjustable coupler, wherein the first selected quantum bit and the second selected quantum bit are any two quantum bits in the plurality of adjacent quantum bits. And then obtaining first crosstalk of the quantum bit to be measured on the virtual quantum bit, wherein the quantum bit to be measured is any one quantum bit of the adjacent quantum bits or the non-adjacent quantum bits. And finally, acquiring second crosstalk of the quantum bit to be detected to the adjustable coupler based on the first crosstalk. The scheme for constructing the virtual quantum bit can effectively test the influence of adjacent and non-adjacent quantum bits on the crosstalk of the adjustable coupler, and fills the blank of the prior art.
The testing device, the quantum control system, the quantum computer and the readable storage medium of the quantum chip provided by the invention belong to the same conception as the testing method of the quantum chip, so that the testing device and the quantum control system have the same beneficial effects and are not repeated herein.
Drawings
Fig. 1 is a schematic structural diagram of a quantum chip according to an embodiment of the present invention;
fig. 2 is a flow chart of a method for testing a quantum chip according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a testing device for a quantum chip according to another embodiment of the present invention.
Detailed Description
Specific embodiments of the present invention will be described in more detail below with reference to the drawings. Advantages and features of the invention will become more apparent from the following description and claims. It should be noted that the drawings are in a very simplified form and are all to a non-precise scale, merely for convenience and clarity in aiding in the description of embodiments of the invention.
In the description of the present invention, it should be understood that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", etc., are based on the directions or positional relationships shown in the drawings, are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.
For better understanding of the technical solutions of the present application, the following briefly describes the related technologies related to the present application:
the Ramsey experiment refers to applying two pi/2 quantum logic gates (i.e. X/2 gates) to a qubit, wherein the time interval between the two operations is tau, and simultaneously applying a read pulse to the qubit after the second pi/2 quantum logic gate operation to obtain the excited state distribution P of the qubit 1 (τ) and varying the time interval τ to obtain P 1 (τ) a process. The result of a typical Ramsey experiment is P 1 (τ) is a mathematical model that satisfies the exponential oscillation decay over time interval τ as follows:
in formula 1, A and B are fitting coefficients, T 0 For decoherence time of qubits, f d Carrier frequency f of microwave pulse signal corresponding to pi/2 quantum logic gate operation 0 Is the oscillation frequency of the qubit, and f 0 True frequency f of the qubit q Carrier frequency of pi/2 quantum logic gate operation satisfies:
f 0 (f d )＝|f q -f d | (2)
from the above, in combination with equation 2, we can get: the result of the Ramsey experiment, namely the oscillation frequency of the curve is equal to the difference between the carrier frequency of the quantum logic gate operation and the real frequency of the quantum bit, so that the Ramsey experiment can be used for obtaining the decoherence time of the quantum bit and can also accurately obtain the real frequency of the quantum bit.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a quantum chip according to an embodiment of the present application, in a quantum chip system including an adjustable coupler, the structure of the adjustable coupler is substantially identical to that of a qubit, and the difference is that the adjustable coupler lacks a reading cavity for reading quantum state information and a quantum state modulation line for adjusting and controlling a quantum state. In the quantum chip, we generally refer to the quantum state modulation line as XY line, and the frequency modulation line, that is, the magnetic flux modulation line, as Z line. The frequency modulation line comprises an AC modulation line and a DC modulation line, the AC modulation line is used for applying an AC signal, the DC modulation line is used for applying a DC signal, and the AC modulation line and the DC modulation line are matched to realize accurate regulation and control of quantum states. When an AC signal is applied to the AC control line of the qubit, in addition to affecting the frequency of the qubit, this phenomenon is called AC crosstalk, and according to the foregoing description, since the tunable coupler is substantially identical to the structure of the qubit, when an AC signal is applied to the frequency modulation line of the qubit, we also affect the frequency of the surrounding tunable coupler, that is, the qubit also affects the AC crosstalk of the tunable coupler, so that, in order to better utilize the qubit, the AC crosstalk between the tunable coupler and the qubit needs to be tested and calibrated before the quantum chip is formally put on line.
Referring to fig. 2, an embodiment of the present invention provides a method for testing a quantum chip, where the quantum chip includes an adjustable coupler, a plurality of adjacent qubits having a direct coupling connection relationship with the adjustable coupler, and a plurality of non-adjacent qubits not having a direct coupling relationship, the method includes:
s1: constructing a virtual qubit based on a quantum state modulation line of a first selected qubit, a quantum state modulation line of a second selected qubit, a reading cavity of the second selected qubit and the adjustable coupler, wherein the first selected qubit and the second selected qubit are any two qubits in the plurality of adjacent qubits;
s2: acquiring first crosstalk of a quantum bit to be detected on the virtual quantum bit, wherein the quantum bit to be detected is any one quantum bit of the adjacent quantum bits or the non-adjacent quantum bits;
s3: and acquiring second crosstalk of the quantum bit to be detected to the adjustable coupler based on the first crosstalk.
The method for testing the quantum chip is characterized in that the virtual quantum bit is constructed based on the quantum state modulation line of the first selected quantum bit, the quantum state modulation line of the second selected quantum bit, the reading cavity of the second selected quantum bit and the adjustable coupler, and the first selected quantum bit and the second selected quantum bit are any two quantum bits in the plurality of adjacent quantum bits. And then obtaining first crosstalk of the quantum bit to be measured on the virtual quantum bit, wherein the quantum bit to be measured is any one quantum bit of the adjacent quantum bits or the non-adjacent quantum bits. And finally, acquiring second crosstalk of the quantum bit to be detected to the adjustable coupler based on the first crosstalk. The scheme for constructing the virtual quantum bit can effectively test the influence of adjacent and non-adjacent quantum bits on the crosstalk of the adjustable coupler, and fills the blank of the prior art.
Taking the quantum chip structure shown in fig. 1 as an example, in this embodiment, the virtual qubit may be formed by using the quantum state modulation line XY1 of the qubit Q1, the quantum state modulation line XY2 of the qubit Q2, the reading cavity of the qubit Q2, and the tunable coupler C, and may also be formed by using the quantum state modulation line XY2 of the qubit Q2, the quantum state modulation line XY1 of the qubit Q1, the reading cavity of the qubit Q1, and the tunable coupler C, and it should be noted that in other embodiments, the number of adjacent qubits directly coupled by the tunable coupler is not necessarily only two, but may be three, four, or even more, so in other embodiments, the virtual qubit may be formed in other forms, which are not described herein in detail. The qubit to be measured may be selected from adjacent qubit Q1 or qubit Q2, and may be selected from non-adjacent qubit QN, which is not limited herein. Those skilled in the art will understand that the quantum chip generally includes a plurality of tunable couplers and a plurality of qubits, and the configuration of virtual qubits in the AC crosstalk obtaining scheme between other tunable couplers and qubits can be similar, which is not described herein.
Specifically, in an embodiment of the present invention, the obtaining the first crosstalk of the qubit to be measured to the virtual qubit includes:
when a second AC signal is in different values, a plurality of AC modulation spectrums corresponding to the virtual quantum bits are obtained, wherein the second AC signal is a signal applied to a frequency modulation line of the quantum bits to be detected;
and acquiring the first crosstalk based on the acquired plurality of AC modulation spectrums.
It will be appreciated by those skilled in the art that the AC modulation spectrum of the virtual qubit referred to herein actually refers to the AC modulation spectrum of the tunable coupler, and since the tunable coupler has been described above as having no reading cavity, a brief description will be made of the principle of how the frequency of the tunable coupler can be indirectly obtained by using the qubit coupled to the tunable coupler, specifically:
a qubit and an adjustable coupler may form a three-level system comprising three basis vectors |00>、|01>And |10>Wherein, |αβ>Representing the qubit occupancy as |alpha>The adjustable coupler occupies |beta>. In the three-energy level system, the quantum bit is loaded with one period driving, and the I00 can be used for>And |10>Coupled together. Furthermore, |01>And |10>The coupling strength between the two is g. The frequencies of the three energy levels are omega respectively 00 ＝0、ω 10 Omega, omega 01 . Here ω 10 ＝f 10 ，ω 01 ＝f 01 Wherein f 10 For the frequency of the qubit, f 01 Is the frequency of the adjustable coupler.
The hamilton consisting of the subspaces of 10> and 01> is:
the two eigenstates of the three-energy-level system are respectively:
the corresponding two eigenvalues are respectively:
where Δ=ω 01 -ω 10 At |01>And |10>In the case of equal energy, at this time When ω=ω 10 At this time, the three-level system cannot be operated by |00>Excited to |10>And when ω=e +(-) ＝ω 10 At + (-) g, the three-level system may consist of |00>Respectively excite to I+>(|+>) The method comprises the steps of carrying out a first treatment on the surface of the At |01>And |10>In the case of far detuning of energy, for example, delta > 0, |phi> ± ≈|10>(|01>) Then it can pass through ω=ω 10 -g 2 The three-energy level system is formed by |00 by delta>Excited to |10>。
Based on the above description, the applicant has further studied to find that when the equivalent qubit does not resonate with the frequency of the tunable coupler, if we excite the qubit, only one excitation frequency can excite the qubit, essentially because only one of the corresponding eigenstates contains a larger |10>. When the frequency of the equivalent qubit is equal to that of the adjustable coupler, namely resonance occurs, the qubit is excited at the moment, and bit excitation can be realized at different frequencies, and the essence is that two eigenstates comprise larger |10>. By utilizing the principle, the frequency and the corresponding AC voltage of the adjustable coupler can be indirectly obtained, and further, the AC modulation spectrum of the adjustable coupler can be indirectly obtained.
Specifically, in the embodiment of the present invention, the AC modulation spectrum of the virtual qubit is obtained by:
the method further includes adjusting a size of a first AC signal to obtain an AC modulation spectrum of the virtual qubit, the first AC signal being a signal applied on a frequency modulation line of the tunable coupler.
Further, in an embodiment of the present invention, the adjusting the size of the first AC signal to obtain the AC modulation spectrum of the virtual qubit includes:
performing a Ramsey experiment on the virtual qubit, applying the first AC signal to a frequency modulation line of the tunable coupler between two pi/2 gates of the Ramsey experiment, and applying the second AC signal to a frequency modulation line of the qubit to be tested so as to cause the qubit to be tested to have a crosstalk effect on the virtual qubit, wherein the two pi/2 gates of the Ramsey experiment are applied to a quantum state modulation line of the first selected qubit;
applying a pulse signal for changing a quantum state to the quantum state modulation line of the second selected qubit;
acquiring the bit frequency corresponding to the virtual quantum bit when the first AC signal is based on a Ramsey experiment result;
when the first AC signal is not traversed in a preset range, adjusting the size of the first AC signal, and returning to execute the Ramsey experiment on the virtual quantum bit;
and acquiring the AC modulation spectrum of the virtual quantum bit based on the acquired first AC signal and the corresponding bit frequency, wherein the AC modulation spectrum of the virtual quantum bit is the AC modulation spectrum of the adjustable coupler.
Specifically, in an embodiment of the present invention, the acquiring the first crosstalk based on the acquired plurality of AC modulation spectrums includes:
acquiring a first crosstalk coefficient based on the acquired plurality of AC modulation spectrums, wherein the first crosstalk coefficient reflects the change condition of the AC modulation spectrums along with the second AC signal;
the first crosstalk coefficient is the first crosstalk.
Specifically, in an embodiment of the present invention, the obtaining, based on the obtained plurality of AC modulation spectrums, a first crosstalk coefficient includes:
acquiring a physical model of an AC modulation spectrum of the virtual qubit, wherein the physical model is used for reflecting the expected situation that the bit frequency of the virtual qubit changes along with the first AC signal;
fitting the acquired AC modulation spectrums based on the physical model;
and acquiring the first crosstalk coefficient based on the fitting processing result.
Further, the applicant proposes a physical model for reflecting the overdue condition of the bit frequency of the virtual qubit as a function of the first AC signal, the physical model being:
wherein Φ=pi M (x-offset);
x is the value of the first AC signal, y is the bit frequency of the virtual qubit, A, M, d and offset are parameters of the physical model, and α is the non-harmonic parameter value of the virtual qubit. It will be appreciated by those skilled in the art that the present application proposes a model with parameters, i.e. parameters in the physical model are not fixed unique, but rather values fitted according to the actual experimental results.
Specifically, in an embodiment of the present invention, the fitting processing for each acquired AC modulation spectrum based on the physical model includes:
fitting each AC modulation spectrum by using the physical model;
acquiring the value of the offset corresponding to each AC modulation spectrum after fitting;
and acquiring the relation between each second AC signal and the value of the corresponding offset as a first relation.
Further, in this embodiment, the acquiring the relationship between each of the second AC signals and the value of the corresponding offset is a first relationship, including:
and fitting a relation of the offset along with the change of the second AC signal into a coordinate system of which the abscissa and the ordinate are the second AC signal and the offset respectively, wherein the relation is a first relation.
It should be noted that by fitting the offset and the second AC signal in the coordinate system, a slope of the slope, i.e. the first relation, and a slope, i.e. the following first crosstalk coefficient, can be obtained.
Optionally, the obtaining the first crosstalk coefficient based on a result of the fitting process includes:
the first crosstalk coefficient is obtained based on the first relationship.
It will be appreciated by those skilled in the art that the first crosstalk coefficient is actually the crosstalk coefficient of the qubit under test to the tunable coupler.
It should be noted that the above solution for obtaining the first crosstalk coefficient is only an embodiment with a preferred effect in the present application, and other embodiments of the present application may also be implemented by adopting other solutions. For example, the first crosstalk coefficient may be obtained by using an AC modulation spectrum of the virtual quantum bit obtained in advance, obtaining a relationship between a difference value between an actual frequency and a theoretical frequency of the virtual quantum bit and a second AC signal applied to the quantum bit to be measured, fitting a slope of the relationship to obtain the first crosstalk coefficient, for example, obtaining the theoretical frequency of the virtual quantum bit when the first voltage is obtained by using the AC modulation spectrum, applying a second AC signal to the quantum bit to be measured, obtaining the actual frequency of the virtual quantum bit by using a Ramsey experiment to obtain the second frequency, obtaining a difference value between the second frequency and the first frequency to be the first difference value, adjusting the size of the second AC signal, measuring the actual frequency of the virtual quantum bit, and so on, we can obtain a plurality of sets of data, each set of data includes a second AC signal and a corresponding first difference value, and then process the data, and fitting a slope k to obtain the slope k, which is the first crosstalk coefficient.
Referring to fig. 3, based on the same inventive concept, an embodiment of the present invention further provides a testing device for a quantum chip, where the quantum chip includes an adjustable coupler, a plurality of adjacent quantum bits having a direct coupling connection relationship with the adjustable coupler, and a plurality of non-adjacent quantum bits not having a direct coupling relationship, and the testing method includes:
a virtual qubit construction module configured to construct a virtual qubit based on a quantum state modulation line of a first selected qubit, a quantum state modulation line of the second selected qubit, a reading cavity of the second selected qubit, and the tunable coupler, the first selected qubit and the second selected qubit being any two qubits of the number of adjacent qubits;
a first crosstalk acquisition module configured to acquire a first crosstalk of a quantum bit to be measured to the virtual quantum bit, the quantum bit to be measured being any one of the plurality of adjacent quantum bits or the plurality of non-adjacent quantum bits;
and the second crosstalk acquisition module is configured to acquire second crosstalk of the quantum bit to be measured to the tunable coupler based on the first crosstalk.
It is understood that the virtual qubit construction module 100, the first crosstalk acquisition module 200, and the second crosstalk acquisition module 300 may be combined in one device to be implemented, or any one of the modules may be split into a plurality of sub-modules, or at least part of the functions of one or more of the virtual qubit construction module 100, the first crosstalk acquisition module 200, and the second crosstalk acquisition module 300 may be combined with at least part of the functions of the other modules and implemented in one functional module. According to embodiments of the present invention, at least one of the virtual qubit construction module 100, the first crosstalk acquisition module 200, and the second crosstalk acquisition module 300 may be implemented at least in part as hardware circuitry, such as a Field Programmable Gate Array (FPGA), a Programmable Logic Array (PLA), a system on a chip, a system on a substrate, a system on a package, an Application Specific Integrated Circuit (ASIC), or any other reasonable manner of integrating or packaging circuitry, or in hardware or firmware, or in a suitable combination of software, hardware, and firmware implementations. Alternatively, at least one of the virtual qubit construction module 100, the first crosstalk acquisition module 200, and the second crosstalk acquisition module 300 may be at least partially implemented as computer program modules, which when run by a computer, may perform the functions of the respective modules.
Based on the same inventive concept, the embodiment of the invention also provides a quantum control system, which tests the quantum chip by using the testing method of the quantum chip described in any one of the above feature descriptions, or the testing device of the quantum chip described in the above feature descriptions.
Based on the same inventive concept, the embodiment of the invention also provides a quantum computer, which comprises the quantum control system described in the above characteristic description.
Based on the same inventive concept, the embodiment of the present invention further provides a readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, can implement the method for testing the quantum chip according to any one of the above feature descriptions.
The readable storage medium may be a tangible device that can hold and store instructions for use by an instruction execution device, such as, but not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the preceding. More specific examples (a non-exhaustive list) of the readable storage medium would include the following: portable computer disks, hard disks, random Access Memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static Random Access Memory (SRAM), portable compact disk read-only memory (CD-ROM), digital Versatile Disks (DVD), memory sticks, floppy disks, mechanical coding devices, punch cards or in-groove structures such as punch cards or grooves having instructions stored thereon, and any suitable combination of the foregoing. The computer program described herein may be downloaded from a readable storage medium to a respective computing/processing device or to an external computer or external storage device via a network, such as the internet, a local area network, a wide area network, and/or a wireless network. The network may include copper transmission cables, fiber optic transmissions, wireless transmissions, routers, firewalls, switches, gateway computers and/or edge servers. The network interface card or network interface in each computing/processing device receives the computer program from the network and forwards the computer program for storage in a readable storage medium in the respective computing/processing device. Computer programs for carrying out operations of the present invention may be assembly instructions, instruction Set Architecture (ISA) instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, c++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The computer program may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any kind of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or may be connected to an external computer (for example, through the Internet using an Internet service provider). In some embodiments, aspects of the present invention are implemented by personalizing electronic circuitry, such as programmable logic circuits, field Programmable Gate Arrays (FPGAs), or Programmable Logic Arrays (PLAs), with state information for a computer program, which can execute computer-readable program instructions.
Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, systems, and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer programs. These computer programs may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the programs, when executed by the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer programs may also be stored in a readable storage medium that can direct a computer, programmable data processing apparatus, and/or other devices to function in a particular manner, such that the readable storage medium storing the computer program includes an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.
The computer program may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the computer program which is executed on the computer, other programmable apparatus or other devices implements the functions/acts specified in the flowchart and/or block diagram block or blocks.
In the description of the present specification, a description of the terms "one embodiment," "some embodiments," "examples," or "particular examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments. Further, one skilled in the art can engage and combine the different embodiments or examples described in this specification.
The foregoing is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any person skilled in the art will make any equivalent substitution or modification to the technical solution and technical content disclosed in the invention without departing from the scope of the technical solution of the invention, and the technical solution of the invention is not departing from the scope of the invention.
Claims (14)
1. A method of testing a quantum chip, the quantum chip comprising an adjustable coupler and a number of adjacent qubits in direct coupling connection with the adjustable coupler and a number of non-adjacent qubits in no direct coupling connection, the method comprising:
constructing a virtual qubit based on a quantum state modulation line of a first selected qubit, a quantum state modulation line of a second selected qubit, a reading cavity of the second selected qubit and the adjustable coupler, wherein the first selected qubit and the second selected qubit are any two qubits in the plurality of adjacent qubits;
acquiring first crosstalk of a quantum bit to be detected on the virtual quantum bit, wherein the quantum bit to be detected is any one quantum bit of the adjacent quantum bits or the non-adjacent quantum bits;
and acquiring second crosstalk of the quantum bit to be detected to the adjustable coupler based on the first crosstalk.
2. The method of testing of claim 1, wherein the obtaining the first crosstalk of the qubit to be tested to the virtual qubit comprises:
when a second AC signal is in different values, a plurality of AC modulation spectrums corresponding to the virtual quantum bits are obtained, wherein the second AC signal is a signal applied to a frequency modulation line of the quantum bits to be detected;
and acquiring the first crosstalk based on the acquired plurality of AC modulation spectrums.
3. The test method of claim 2, wherein the AC modulation spectrum of the virtual qubit is obtained by:
the method further includes adjusting a size of a first AC signal to obtain an AC modulation spectrum of the virtual qubit, the first AC signal being a signal applied on a frequency modulation line of the tunable coupler.
4. The test method of claim 3, wherein the resizing the first AC signal to obtain the AC modulation spectrum of the virtual qubit comprises:
performing a Ramsey experiment on the virtual qubit, applying the first AC signal to a frequency modulation line of the tunable coupler between two pi/2 gates of the Ramsey experiment, and applying the second AC signal to a frequency modulation line of the qubit to be tested so as to cause the qubit to be tested to have a crosstalk effect on the virtual qubit, wherein the two pi/2 gates of the Ramsey experiment are applied to a quantum state modulation line of the first selected qubit;
applying a pulse signal for changing a quantum state to the quantum state modulation line of the second selected qubit;
acquiring the bit frequency corresponding to the virtual quantum bit when the first AC signal is based on a Ramsey experiment result;
when the first AC signal is not traversed in a preset range, adjusting the size of the first AC signal, and returning to execute the Ramsey experiment on the virtual quantum bit;
and acquiring the AC modulation spectrum of the virtual quantum bit based on the acquired first AC signal and the corresponding bit frequency, wherein the AC modulation spectrum of the virtual quantum bit is the AC modulation spectrum of the adjustable coupler.
5. The test method of claim 3, wherein the acquiring the first crosstalk based on the acquired plurality of AC modulation spectra comprises:
acquiring a first crosstalk coefficient based on the acquired plurality of AC modulation spectrums, wherein the first crosstalk coefficient reflects the change condition of the AC modulation spectrums along with the second AC signal;
the first crosstalk coefficient is the first crosstalk.
6. The method of testing of claim 5, wherein the obtaining a first crosstalk coefficient based on the obtained plurality of AC modulation spectra comprises:
acquiring a physical model of an AC modulation spectrum of the virtual qubit, wherein the physical model is used for reflecting the expected situation that the bit frequency of the virtual qubit changes along with the first AC signal;
fitting the acquired AC modulation spectrums based on the physical model;
and acquiring the first crosstalk coefficient based on the fitting processing result.
7. The test method of claim 6, wherein the physical model is:
wherein Φ=pi M (x-offset);
x is the value of the first AC signal, y is the bit frequency of the virtual qubit, A, M, d and offset are parameters of the physical model, and α is the non-harmonic parameter value of the virtual qubit.
8. The test method of claim 7, wherein fitting the acquired AC modulation spectra based on the physical model comprises:
fitting each AC modulation spectrum by using the physical model;
acquiring the value of the offset corresponding to each AC modulation spectrum after fitting;
and acquiring the relation between each second AC signal and the value of the corresponding offset as a first relation.
9. The method of testing of claim 8, wherein the obtaining the relationship between each of the second AC signals and the value of the corresponding offset is a first relationship, comprising:
and fitting a relation of the offset along with the change of the second AC signal into a coordinate system of which the abscissa and the ordinate are the second AC signal and the offset respectively, wherein the relation is a first relation.
10. The test method of claim 9, wherein the obtaining the first crosstalk coefficient based on the result of the fitting process comprises:
the first crosstalk coefficient is obtained based on the first relationship.
11. A device for testing a quantum chip, the quantum chip comprising an adjustable coupler and a plurality of adjacent qubits in direct coupling connection with the adjustable coupler and a plurality of non-adjacent qubits in non-direct coupling connection, the method comprising:
a virtual qubit construction module configured to construct a virtual qubit based on a quantum state modulation line of a first selected qubit, a quantum state modulation line of the second selected qubit, a reading cavity of the second selected qubit, and the tunable coupler, the first selected qubit and the second selected qubit being any two qubits of the number of adjacent qubits;
a first crosstalk acquisition module configured to acquire a first crosstalk of a quantum bit to be measured to the virtual quantum bit, the quantum bit to be measured being any one of the plurality of adjacent quantum bits or the plurality of non-adjacent quantum bits;
and the second crosstalk acquisition module is configured to acquire second crosstalk of the quantum bit to be measured to the tunable coupler based on the first crosstalk.
12. A quantum control system, characterized in that a quantum chip is tested by the testing method of a quantum chip according to any one of claims 1-10, or a testing device comprising a quantum chip according to claim 11.
13. A quantum computer comprising the quantum control system of claim 12.
14. A readable storage medium having stored thereon a computer program, which when executed by a processor is capable of implementing the method of testing a quantum chip according to any of claims 1 to 10.
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