Method and system for decomposing single-qubit quantum circuits into a discrete basis

Patent metadata

Field	Value
Publication number	US-9514415-B2
Application number	US-201314018319-A
Country	US
Kind code	B2
Filing date	Sep 4, 2013
Priority date	Mar 15, 2013
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

A target quantum circuit expressed in a first quantum gate basis may be transformed into a corresponding quantum circuit expressed in a second quantum gate basis, which may be a universal set of gates such as a V gate basis set. The target quantum circuit may be expressed as a linear combination of quantum gates. The linear combination of quantum gates may be mapped to a quaternion. The quaternion may be factorized, based at least in part on an amount of precision between the target quantum circuit and the corresponding quantum circuit expressed in the second quantum gate basis, into a sequence of quaternion factors. The sequence of quaternion factors may be mapped into a sequence of quantum gates of the second quantum gate basis, where the sequence of sequence of quantum gates is the corresponding quantum circuit.

First claim

The invention claimed is:

1. A method for performing quantum calculations, the method comprising:
mapping a unitary corresponding to a target quantum gate to a quaternion;
factoring the quaternion into a sequence of irreducible quaternion factors;
mapping the sequence of irreducible quaternion factors into a sequence of quantum gates of a universal basis set; and
applying the sequence of quantum gates to a target qubit.

2. The method of claim 1 , further comprising:
determining an amount of precision between the sequence of quantum gates and the target quantum gate; and
expressing the unitary as a linear combination of elemental gates of the set of universal basis gates, wherein coefficients of the linear combination of elemental gates are a function of the amount of precision.

3. The method of claim 2 , wherein the coefficients of the linear combination of elemental gates includes a first coefficient and other coefficients, the method further comprising:
randomly picking a value of the first coefficient; and
determining whether values of the other coefficients exist subject to a constraint imposed by a unitarity condition for the coefficients of the linear combination of elemental gates.

4. The method of claim 2 , further comprising:
directly searching for values of the coefficients of the linear combination of elemental gates that exist subject to a constraint imposed by the amount of precision.

5. The method of claim 4 , wherein the coefficients of the linear combination of elemental gates includes a first pair of coefficients and a second pair of coefficients, and wherein directly searching for values of the coefficients of the linear combination of elemental gates further comprises:
sweeping over pairs of integer values for the first pair of coefficients;
building a hash table based at least in part on a constraint imposed by the amount of precision and the swept over pairs of integer values; and
for multiple candidate pairs of integer values, sweeping over the hash table for a specific value corresponding to a respective candidate pair of integer values, wherein the respective candidate pair of integer values are the second pair of coefficients subject to the specific value being in the hash table.

6. The method of claim 5 , wherein the respective candidate pair of integer values is comprised of a first integer and a second integer, and wherein the specific value corresponding to the respective candidate pair of integer values is equal to a sum of the first integer squared and the second integer squared.

7. The method of claim 5 , wherein building the hash table based at least in part on the constraint imposed by the amount of precision and the swept over pairs of integer values comprises, for each swept over pair of integers,
determining a sum of squares of integers in the pair of integers;
determining a difference between the sum of squares and parameter that is a function of the amount of precision; and
including the difference in the hash table.

8. The method of claim 1 , further comprising:
storing the sequence of quantum gates of the universal basis set in a storage device.

9. A quantum circuit comprising:
a sequence of quantum gates of a universal basis set that correspond to a target quantum gate, wherein the sequence of quantum gates is made by a process comprising:
mapping a unitary corresponding to the target quantum gate to a quaternion;
factoring the quaternion into a sequence of irreducible quaternion factors; and
mapping the sequence of irreducible quaternion factors into the sequence of quantum gates of the universal basis set.

10. The quantum circuit of claim 9 , wherein the process further comprises:
determining an amount of precision between the sequence of quantum gates and the target quantum gate; and
expressing the unitary as a linear combination of elemental gates of the set of universal basis gates, wherein coefficients of the linear combination of elemental gates are a function of the amount of precision.

11. The quantum circuit of claim 10 , wherein the coefficients of the linear combination of elemental gates include a first coefficient and other coefficients, and wherein the process further comprises:
randomly picking a value of the first coefficient; and
determining whether values of the other coefficients exist subject to a constraint imposed by a unitarity condition for the coefficients of the linear combination of elemental gates.

12. The quantum circuit of claim 10 , wherein the process further comprises:
directly searching for values of the coefficients of the linear combination of elemental gates that exist subject to a constraint imposed by the amount of precision.

13. The quantum circuit of claim 12 , wherein the coefficients of the linear combination of elemental gates includes a first pair of coefficients and a second pair of coefficients, and wherein directly searching for values of the coefficients of the linear combination of elemental gates further comprises:
sweeping over pairs of integer values for the first pair of coefficients;
building a hash table based at least in part on a constraint imposed by the amount of precision and the swept over pairs of integer values; and
for multiple candidate pairs of integer values, sweeping over the hash table for a specific value corresponding to a respective candidate pair of integer values, wherein the respective candidate pair of integer values are the second pair of coefficients subject to subject to the specific value being in the hash table.

14. The quantum circuit of claim 13 , wherein the respective candidate pair of integer values is comprised of a first integer and a second integer, and wherein the specific value corresponding to the respective candidate pair of integer values is equal to a sum of the first integer squared and the second integer squared.

15. The quantum circuit of claim 13 , wherein building the hash table based at least in part on the constraint imposed by the amount of precision and the swept over pairs of integer values comprises, for each swept over pair of integers,
determining a sum of squares of integers in the pair of integers;
determining a difference between the sum of squares and parameter that is a function of the amount of precision; and
including the difference in the hash table.

16. A system for quantum-circuit design comprising:
a processor;
a computer readable storage device storing instructions, wherein the instructions, when executed by the processor, cause the processor to perform acts comprising,
mapping a unitary corresponding to a target quantum gate to a quaternion;
factoring the quaternion into a sequence of irreducible quaternion factors;
mapping the sequence of quaternion factors into a sequence of quantum gates of a universal basis set; and
storing the sequence of quantum gates into the computer-readable storage device.

17. The system of claim 16 , wherein acts performed by the processor further include:
determining an amount of precision between the sequence of quantum gates and the target quantum circuit; and
expressing the unitary as a linear combination of elemental gates of the set of universal basis gates, wherein coefficients of the linear combination of elemental gates are a function of the amount of precision.

18. The system of claim 17 , wherein the coefficients of the linear combination of elemental gates includes a first coefficient and other coefficients, the method further comprising:
randomly picking a value of the first coefficient; and

Assignees

• Microsoft Corp
• Microsoft Technology Licensing Llc

Inventors

• Bocharov Alexei V
• Gurevich Yuri
• Svore Krysta M

Classifications

• G06N99/002 Primary

  Physics · mapped topic

• B82Y10/00

  Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic · CPC title

• G06N10/60 Primary

  Quantum algorithms, e.g. based on quantum optimisation, quantum Fourier or Hadamard transforms · CPC title