Method and system for characteristic evaluation and calibration for quantum processor

Abstract

To provide a computer mounting method, a system, and a quantum circuit, for performing characteristic evaluation for target error parameters of an execution error in quantum logic operations g acting on a target set of quantum bits of a quantum processor.SOLUTION: A method includes a step 210 of generating at least one characteristic evaluation sequence S213 configured to amplify at least one target error parameter. The at least one characteristic evaluation sequence includes at least one refocus sequence R217. The at least one refocus sequence includes the characteristic evaluation sequence configured to reduce a predetermined generator term including a crosstalk between a target set of quantum bits and another set of the quantum bits of a quantum processor. The method also includes a step 220 of using the at least one characteristic evaluation sequence to perform characteristic evaluation for at least one target error parameter θ in a characteristic evaluation protocol.SELECTED DRAWING: Figure 2

Claims

1. 1. A computer-implemented method for characterizing at least one target error parameter of an execution error in a quantum logic operation g operating on a target set of qubits of a quantum processor, the method comprising: (a) generating at least one characterization sequence S configured to amplify the at least one target error parameter, the at least one characterization sequence S including at least one refocus sequence, the at least one refocus sequence configured to reduce a predetermined generator term comprising crosstalk between a target set of qubits and another set of qubits of the quantum processor; (b) characterizing the at least one target error parameter using the at least one characterization sequence in a characterization protocol; and 4. A computer-implemented method comprising:

2. (a) the at least one characterization sequence S is configured to reduce a predetermined coherent error generator term in a target set of qubits; (b) the method characterizes a single target error parameter of an execution error in the quantum logic operation g; (c) the at least one target error parameter is a Pauli generator term P ｔ and the at least one characterization sequence S is configured to remove a predetermined Pauli generator term of the run-time error separate from the at least one target error parameter; (d) the at least one refocusing sequence is ｔ The method of claim 1 , wherein

3. The method of claim 1 , wherein the at least one refocusing sequence is one of a dynamic decoupling sequence and a twirling sequence.

4. 2. The method of claim 1, wherein the at least one characterization sequence S is configured to either reduce a magnitude measure of the crosstalk or remove at least a first order error of a run-time error separate from the at least one target error parameter.

5. The at least one refocus sequence may include a set of refocus sequences, and the at least one characterization sequence S may include a concatenation of a predetermined number n of refocus sequences. [0010] where k=0, 1 , . . . , n-1, [0025] is a refocus sequence included in the set of refocus sequences, and G ０ The method of claim 1 , wherein: = g, g is the quantum logic operation.

6. The at least one characterization sequence S includes at least one reference motion; (a) the at least one reference operation includes a state preparation operation configured to set a state of the set of qubits to a prepared Pauli state Pp; (b) the at least one reference motion is a measured Pauli P ｍ measuring the set of qubits according to (c) The preparation Pauli state P ｐ and measured Pauli P ｍ is configured to increase the sensitivity of the at least one characterization sequence S to the at least one error parameter; (d) The preparatory Pauli state P ｐ , measured Pauli P ｍ and the Pauli generator term P ｔ 3. The method of claim 2, wherein x is over an algebra isomorphic to a SU(2) Lie algebra.

7. The quantum logic operation g is a two-qubit operation, (a) The Pauli generator term P ｔ commutates back with at least one generator of the KAK decomposition of an ideal version of the quantum logical operation g; (b) The sum of the coefficients is [0030] is greater than the Pauli generator term P ｔ corresponding to the at least one KAK generator that exchanges back with (c) the at least one refocus sequence includes at least one secondary refocus sequence, the at least one secondary refocus sequence being a function of the Pauli generator term P ｔ 2. The method of claim 1, wherein the quantum logic operation g is replaced by all commutators of and generators of the KAK decomposition of an ideal version of the quantum logic operation g.

8. (a) The Pauli generator term P ｔ is separate from the overrotation term, where i) the recursively concatenated germ comprises at least n concatenation steps; ii) the Pauli generator term P ｔ is separate from the overrotation terms, and the first-order refocusing sequence backcommutes with the corresponding Pauli generator terms of the ideal version of the quantum logic operation g, iii) The at least one characterization sequence S is a 1-2 Pauli generator term of the execution error －ｎ configured to remove a portion of (b) the Pauli generator term P ｔ is an overrotation term, the recursively connected germ includes at least n connection steps, and the at least one characterization sequence S is a 1-2 Pauli generator term of the execution error. －（ｎ＋１） configured to remove a portion of and the at least one characterization sequence S preferably includes the Pauli generator term P ｔ The method of claim 5 , configured to separate

9. (a) The Pauli generator term P ｔ is an overrotation term, and the at least one characterization sequence S is a germ [0045] wherein A, B, and C are refocus sequences; (b) the Pauli generator term P ｔ is separate from the over-rotation term, and the at least one characterization sequence S is [0050] where A, B, and C are refocusing sequences; The method of claim 8, comprising any one of the following:

10. (a) The Pauli generator term P ｔ is separate from the overrotation term, and the at least one characterization sequence S is divided into at least one subsequence G （４） = PgDgDP, where i) P is a randomly sampled Pauli operator; ii) The D is the Pauli generator term P ｔ and back-commuting with the corresponding Pauli generator terms of an ideal version of the quantum logic operation g; (b) the Pauli generator term P ｔ is an overrotation term, and the at least one characterization sequence S is a subsequence of at least one subsequence G （５） = PgP, where P is the Pauli generator term P ｔ is a randomly sampled Pauli operator that commutes with; The method of claim 2 , comprising any one of the following:

11. 2. The method of claim 1 , wherein the at least two quantum logical operations are applied in parallel to at least two quantum logical operations operating on corresponding subsets of qubits, each of the corresponding subsets of qubits having no common qubits.

12. 12. The method of claim 11, wherein there is no crosstalk between each of the corresponding subsets of qubits.

13. 12. The method of claim 11, wherein each of the corresponding subsets of qubits is included in a corresponding hyperedge of an interaction hypergraph, each of the corresponding hyperedges being unique for each of the corresponding subsets of qubits.

14. A non-transitory computer readable storage medium storing computer instructions, the computer instructions being used to cause a computer to perform the method of claim 1.

15. 13. A system comprising a computer and a quantum processor, the computer having gate-level or pulse-level access to the quantum processor and configured to perform the method of claim 1.

16. 1. A quantum circuit for use in characterizing an execution error in a quantum logic operation g operating on a set of quantum bits, the quantum circuit comprising the quantum logic operation g and at least one refocusing sequence, the quantum circuit configured to amplify at least one target error parameter, the at least one refocusing sequence configured to reduce a predetermined term of crosstalk between the set of quantum bits and a set of spectator qubits of the quantum processor, the at least one target error parameter being a Pauli generator term P ｔ wherein the at least one characterization sequence is configured to reduce a predetermined generator term in a target set of qubits.

17. 17. The quantum circuit of claim 16, wherein the at least one refocusing sequence is one of a dynamic decoupling sequence and a twirling sequence.

18. (a) The Pauli generator term P ｔ is not an overrotating Pauli generator term, and the quantum circuit is a germanium [006] where A, B, and C are refocusing sequences; (b) the Pauli generator term P ｔ is the overrotating Pauli generator term, and the quantum circuit is a germanium [0070] wherein A, B, and C are refocus sequences; 17. The quantum circuit of claim 16, comprising any one of:

19. A given number n of concatenations [0080] where k=0,1 , . . . , n-1, where G ０ = g, where [0097] 17. The quantum circuit of claim 16, wherein: is a refocus sequence included in the set of refocus sequences.

20. (a) The Pauli generator term P ｔ is not an overrotated Pauli generator term, and the quantum circuit has at least one subsequence G （３） = PgDgDP, where i) The P is the Pauli generator term P ｔ is a randomly sampled Pauli operator that commutes with ii) The D is the Pauli generator term P ｔ and back-commuting with the corresponding Pauli generator terms of an ideal version of the quantum logic operation g; (b) the Pauli generator term P ｔ is an overrotated Pauli generator term, and the quantum circuit generates at least one subsequence G （４） = PgP, where P is the Pauli generator term P ｔ is a randomly sampled Pauli operator that commutes with; 17. The quantum circuit of claim 16, comprising any one of:

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