Edge-disjoint paths for long-range multi-qubit operations in quantum circuit

Patent metadata

Field	Value
Publication number	US-11734596-B2
Application number	US-202017096313-A
Country	US
Kind code	B2
Filing date	Nov 12, 2020
Priority date	Nov 12, 2020
Publication date	Aug 22, 2023
Grant date	Aug 22, 2023

Abstract

A method for performing long-range multi-qubit measurements in a quantum circuit utilizes a graph that maps qubits of the quantum circuit to nodes that are connected to one another by edges. The method provides for identifying sets of the nodes on the graph corresponding to sets of qubits targeted by multi-qubit operations in a quantum algorithm and for defining a group of edge-disjoint paths connecting the nodes of each set. The group of edge-disjoint paths is defined such that no two of the paths in the group share an edge. The method further provides for performing a set of operations to entangle the qubits corresponding to the to the identified set of nodes that are included in each path in the group and for performing the set of multi-qubit operations on the entangled sets of the qubits.

First claim

What is claimed is:

1. A method comprising:
defining a graph including nodes mapped to qubits in a quantum device, the nodes being connected to each other by edges;
identifying sets of nodes on the graph corresponding to sets of qubits targeted by multi-qubit operations in a quantum algorithm;
defining a group of edge-disjoint paths, each path in the group being defined along one or more edges and nodes and including one of the identified sets of nodes, the group of edge-disjoint paths being defined such that no two of the paths in the group share an edge;
for each defined path, performing a set of operations to entangle the qubits corresponding to the identified set of nodes that are included in the path; and
performing the set of multi-qubit operations on the entangled sets of the qubits.

2. The method of claim 1 , further comprising:
within the defined set of edge-disjoint paths, identifying a subset of the paths that intersect with one another at one or more nodes;
for each path in the identified subset of paths, segmenting the path into one or more first stage segments and one or more second stage segments, the first stage segments and the second stage segments being defined such that no two of first stage segments intersect one another and no two of the second stage segments intersect one another; and
performing entanglement operations associated with the first stage segments at a different point in time than entanglement operations associated with the second stage segment.

3. The method of claim 2 , further comprising:
performing a first set of operations to entangle qubits corresponding to each respective one of the first stage segments;
at a subsequent time, performing a second set of operations to entangle qubits corresponding to each respective one of the second stage segments.

4. The method of claim 3 , wherein performing the first set of operations to entangle the qubits of each respective one of the first stage segments further comprises:
defining even and odd edges in the first stage segment;
for qubits corresponding to each even edge in the first stage segment, performing a joint measurement; and
for qubits corresponding to each odd edge in the first stage segment, performing a joint measurement.

5. The method of claim 3 , wherein performing the first set of operations to entangle the qubits of each respective one of the second stage segments further comprises:
defining even and odd edges in the second stage segment;
for qubits corresponding to each even edge in the second stage segment, performing a joint measurement;
for qubits corresponding to each odd edge in the second stage segment, performing a joint measurement.

6. The method of claim 1 , wherein the qubits in the quantum device are logical qubits implemented in a surface code that is built from physical qubits.

7. The method of claim 1 , wherein performing the set of multi-qubit operations further comprises:
simultaneously performing some or all of the multi-qubit operations.

8. A quantum computing system comprising:
a quantum device that executes circuit definitions to effect parallel multi-qubit operations specified by a quantum algorithm; and
a controller stored in memory and executable to:
access a graph including nodes mapped to the qubits in the quantum device, the nodes of the graph being connected by edges;
identify sets of nodes on the graph corresponding to sets of qubits targeted by the parallel multi-qubit operations;
define a group of edge-disjoint paths, each path in the group being defined along one or more edges and nodes and including one of the identified sets of nodes, the group of edge-disjoint paths being defined such that no two of the paths in the set share an edge;

compile a circuit for execution by the quantum device, the circuit being executable to entangle the qubits corresponding to the identified set of nodes included in each defined path in the group of edge-disjoint paths and to perform the parallel multi-qubit operations.

9. The quantum computing system of claim 8 , wherein the controller is further executable to:
identify a subset of the paths within the group that intersect at one or more nodes;
for each path in the identified subset of paths, segment the path into one or more first stage segments and one or more second stage segments, the first stage segments and the second stage segments being defined such that no two of first stage segments intersect one another and no two of the second stage segments intersect one another,
wherein the compiled circuit is further executable to effect entanglement operations associated with the first stage segments at a different point in time than entanglement operations associated with the second stage segment.

10. The quantum computing system of claim 9 , wherein the controller is further executable to:
generate a first circuit definition for a first circuit executable to effect a first set of operations to entangle qubits corresponding to each respective one of the first stage segments;
generate a second circuit definition for a second circuit executable to effect a second set of operations to entangle qubits corresponding to each respective one of the first stage segments.

11. The quantum computing system of claim 10 , wherein even and odd edges are defined with respect to each one of the first stage segments and the first circuit is further executable to:
perform a joint measurement on qubits corresponding to each of the even edges within the first stage segments; and
perform a joint measurement on qubits corresponding to each of the odd edges within the first stage segments.

12. The quantum computing system of claim 10 , wherein even and odd edges are defined with respect to each one of the second stage segments and the second circuit is further executable to:
perform a joint measurement on qubits corresponding to each of the even edges in the second stage segments; and
perform a joint measurement on qubits corresponding to each of the odd edges within the second stage segments.

13. The quantum computing system of claim 8 , wherein the qubits in the quantum circuit are logical qubits implemented in a surface code built from physical qubits.

14. The quantum computing system of claim 8 , wherein the circuit is further executable to simultaneously execute some or all of the parallel multi-qubit operations.

15. A tangible computer-readable storage medium having instructions stored thereon, wherein the instructions when executed by a processor cause the processor to:
define a graph including nodes mapped to qubits in a quantum device, the nodes of the graph being connected by edges;
identify sets of nodes on the graph corresponding to sets of qubits targeted by multi-qubit operations in a quantum algorithm;
define a group of edge-disjoint paths, each path in the group being defined along one or more edges and nodes and including one of the identified sets of nodes, the group of edge-disjoint paths being defined such that no two of the paths in the group share an edge;
for each defined path, perform a set of operations to entangle the qubits corresponding to the identified set of nodes that are included in the path; and
perform the set of multi-qubit operations on the entangled sets of the qubits.

16. The tangible computer-readable storage media of claim 15 , wherein the instructions further cause the processor to:
identify a subset of the paths within the group that intersect with one another at one or more nodes;
for each path in the identified subset of paths, segment the path into one or mor

Assignees

• Microsoft Technology Licensing Llc

Inventors

• Kliuchnikov Vadym
• Schoute Eddie
• Vaschillo Alexander
• Vasilevsky Dmitry
• Beverland Michael

Classifications

• G06N10/00 Primary

  Quantum computing, i.e. information processing based on quantum-mechanical phenomena · CPC title

• G06F15/82

  data or demand driven · CPC title

• G06F30/327

  Logic synthesis; Behaviour synthesis, e.g. mapping logic, HDL to netlist, high-level language to RTL or netlist · CPC title

• G06N10/60

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

• G06N10/70

  Quantum error correction, detection or prevention, e.g. surface codes or magic state distillation · CPC title