Optical control of atomic quantum bits for phase control of operation

Patent metadata

Field	Value
Publication number	US-11004009-B2
Application number	US-201916239319-A
Country	US
Kind code	B2
Filing date	Jan 3, 2019
Priority date	Jan 4, 2018
Publication date	May 11, 2021
Grant date	May 11, 2021

Abstract

The disclosure describes various aspects of optical control of atomic quantum bits (qubits) for phase control operations. More specifically, the disclosure describes methods for coherently controlling quantum phases on atomic qubits mediated by optical control fields, applying to quantum logic gates, and generalized interactions between qubits. Various attributes and settings of optical/qubit interactions (e.g., atomic energy structure, laser beam geometry, polarization, spectrum, phase, background magnetic field) are identified for imprinting and storing phase in qubits. The disclosure further describes how these control attributes are best matched in order to control and stabilize qubit interactions and allow extended phase-stable quantum gate sequences.

First claim

What is claimed is:

1. A method for optical control of atomic quantum bits (qubits), comprising:
identifying a qubit operation; and
controlling fields in optical beams applied to at least one of the atomic qubits for phase control of the qubit operation, wherein the optical beams are configured in a phase insensitive configuration, and wherein the optical beams include counter-propagating optical beams when the qubit operation is a multi-qubit operation.

2. The method of claim 1 , wherein the optical beams include co-propagating optical beams when the qubit operation is a single qubit operation and is to be motion insensitive.

3. The method of claim 1 , wherein the optical beams include counter-propagating optical beams when the qubit operation is a single qubit operation and is to be motion sensitive.

4. The method of claim 1 , wherein the atomic qubits correspond to atomic ions in a crystal formed by an ion trap.

5. The method of claim 4 , further comprising configuring the optical beams to include up to N individually addressing Raman beams for N atomic ions in the crystal with multiple optical frequencies on each of the individually addressing Raman beams, and a single global counter-propagating Raman beam against the up to N individually addressing Raman beams.

6. The method of claim 1 , wherein the qubit operation is one of multiple qubit operations in an extended quantum computation, and wherein the phase insensitive configuration is used throughout the extended quantum computation.

7. The method of claim 1 , wherein controlling the fields in the optical beams applied to at least one of the atomic qubits for phase control of the qubit operation includes controlling a polarization of the optical beams to compensate for an AC Stark shift of a qubit level in the at least one of the atomic qubits.

8. The method of claim 7 , wherein polarization of the optical beams to compensate for the AC Stark shift is configured to balance the AC Stark shift and enable different types of qubit gates associated with performing the quantum operation.

9. The method of claim 8 , wherein the polarization of the optical beams is a dynamic polarization, a static polarization, or a combination thereof.

10. The method of claim 1 , further comprising configuring the optical beams to be Raman beams, wherein the configuring includes generating the Raman beams from a single optical frequency comb and/or resulting from modulating an optical source, or from multiple phase-coherent sources phase locked, and wherein a phase stability between the multiple tones or teeth of the single optical frequency comb is maintained using a locking technique feeding back directly to the optical source.

11. The method of claim 1 , wherein controlling the fields in the optical beams applied to the at least one of the atomic qubits for phase control of the qubit operation includes additionally controlling one or more of a geometry, a spectrum, or a polarization of the optical beams.

12. The method of claim 1 , wherein the qubit operation is a rotation operation and the optical beams include co-propagating optical beams having a helicity configured to allow the rotation operation while also canceling out at least a portion of an AC Stark shift.

13. The method of claim 12 , wherein the helicity includes an imbalance between σ + polarization versus σ − polarization.

14. A quantum information processing (QIP) system for optical control of atomic quantum bits (qubits), comprising:
one or more optical sources that generate optical beams; and
an optical controller, wherein the optical controller is configured to:
identify a qubit operation; and
control fields in the optical beams applied to at least one of the atomic qubits for phase control of the qubit operation, wherein the optical beams are configured in a phase insensitive configuration, and wherein the optical beams include counter-propagating optical beams when the qubit operation is a multi-qubit operation.

15. The QIP system of claim 14 , wherein the optical beams include co-propagating optical beams when the qubit operation is a single qubit operation and is to be motion insensitive.

16. The QIP system of claim 14 , wherein the optical beams include counter-propagating optical beams when the qubit operation is a single qubit operation and is to be motion sensitive.

17. The QIP system of claim 14 , further comprising an ion trap, wherein the atomic qubits correspond to atomic ions in a crystal formed by the ion trap.

18. The QIP system of claim 14 , wherein the optical controller is further configured to configure the optical beams to include up to N individually addressing Raman beams for N atomic ions in the crystal with multiple optical frequencies on each of the individually addressing Raman beams, and a single global counter-propagating Raman beam against the up to N individually addressing Raman beams.

19. The QIP system of claim 14 , wherein the qubit operation is one of multiple qubit operations in an extended quantum computation, and wherein the phase insensitive configuration is used throughout the extended quantum computation.

20. The QIP system of claim 14 , wherein the optical controller configured to control the fields in the optical beams applied to at least one of the atomic qubits for phase control of the qubit operation is further configured to control a polarization of the optical beams to compensate for an AC Stark shift of a qubit level in the at least one of the atomic qubits.

21. The QIP system of claim 14 , wherein the optical controller is further configured to configure the optical beams to be Raman beams by generating the Raman beams from a single optical frequency comb and/or resulting from modulating an optical source, or from multiple phase-coherent sources phase locked, and wherein a phase stability between the multiple tones or teeth of the single optical frequency comb is maintained using a locking technique feeding back directly to the one optical source.

22. The QIP system of claim 14 , wherein controlling the fields in the optical beams applied to the at least one of the atomic qubits for phase control of the qubit operation includes additionally controlling one or more of a geometry, a spectrum, or a polarization of the optical beams.

23. A quantum information processing (QIP) apparatus for optical control of atomic quantum bits (qubits), comprising:
means for identifying a qubit operation; and
means for controlling fields in optical beams applied to at least one of the atomic qubits for phase control of the qubit operation, wherein the optical beams are configured in a phase insensitive configuration, and wherein the optical beams include counter-propagating optical beams when the qubit operation is a multi-qubit operation.

24. The QIP apparatus of claim 23 , wherein the atomic qubits correspond to atomic ions in a crystal formed by an ion trap.

25. The QIP apparatus of claim 23 , wherein:
the optical beams include co-propagating optical beams when the qubit operation is a single qubit operation and is to be motion insensitive, or
the optical beams include counter-propagating optical beams when the qubit operation is a single qubit operation and is to be motion sensitive.

26. A computer-readable medium storing code with instructions executable by a processor for optical control of atomic quantum bits (qubits), comprising:
code for identifying a qubit

Assignees

• Univ Maryland

Inventors

• Monroe Christopher
• Cetina Marko
• Linke Norbert
• Debnath Shantanu

Classifications

• G06N10/40 Primary

  Physical realisations or architectures of quantum processors or components for manipulating qubits, e.g. qubit coupling or qubit control · CPC title

• G06N10/00 Primary

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

• B82Y10/00

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

• G06E1/00

  Devices for processing exclusively digital data · CPC title