Discrete frequency modulated gates for conditional logic in trapped ion quantum computers

Patent metadata

Field	Value
Publication number	US-12079687-B2
Application number	US-202117212678-A
Country	US
Kind code	B2
Filing date	Mar 25, 2021
Priority date	Mar 26, 2020
Publication date	Sep 3, 2024
Grant date	Sep 3, 2024

Abstract

A system includes a controller configured to reconstitute a continuous waveform to a discrete analogue version. The system includes a numerical optimizer configured to determine frequencies of a pulse sequence. The numerical optimizer uses radial motional mode frequencies and a desired gate time. The numerical optimizer generates the pulse sequence by closing phase-space trajectories, disentangling spins and motions, and constraining a Rabi frequency for motional sideband transitions. The system also includes a display configured to illustrate a discrete frequency modulation pulse sequence based on the determined frequencies.

First claim

What is claimed is:

1. A system comprising:
a controller configured to reconstitute a continuous waveform to a discrete analogue version;
a processor configured to determine frequencies of a pulse sequence for the discrete analogue version, wherein the processor uses radial motional mode frequencies, and a desired gate time, wherein the processor generates the pulse sequence by closing phase-space trajectories for the radial motional modes, and disentangles spins and motion, and constrains a Rabi frequency for motional sideband transitions, wherein a field-programmable gate array is configured to trigger frequency updates for direct digital synthesizer (DDS) channels in real-time based on the determined frequencies to correct any phase deviation that results in amplitude error; and
display configured to illustrate a discrete frequency modulation pulse sequence based on the determined frequencies, wherein the discrete frequency modulation pulse sequence is designed to be a sequence of equal-time segments, wherein each of the equal-time segments have a constant frequency.

2. The system of claim 1 , wherein the desired gate time is less than or equal to two hundred microseconds.

3. The system of claim 1 , wherein processor constrains the Rabi frequency to be less than seven kHz.

4. The system of claim 1 , wherein the processor is configured to correct a drift of the radial motional modes that leads to spin-motion entanglement and deviation from a geometric phase.

5. A system comprising:
a controller is configured to obtain a predetermined gate time and measured mode frequencies;
a processor configured to receive the predetermined gate time and measured mode frequencies to determine frequencies for a pulse sequence, wherein the processor eliminates phase-space trajectories including drift of motional mode frequencies that cause spin-motion entanglement and deviation of a geometric phrase, and wherein the processor constrains a Rabi frequency of motional sideband transitions, wherein a field-programmable gate array is configured to trigger frequency updates for direct digital synthesizer (DDS) channels in real-time based on the determined frequencies to correct any phase deviation that results in amplitude error; and
a display device configured to illustrate the pulse sequence based on the predetermined gate time, measured mode frequencies, and the frequencies determined by eliminating the spin-motion entanglement and deviation from the geometric phase.

6. The system of claim 5 , wherein the deviation of the geometric phase is for a Molmer-Sorenson (MS) two-qubit gate.

7. The system of claim 5 , wherein the processor calculates the frequencies for the pulse sequence to enable the pulse sequence to have equal-time segments.

8. The system of claim 5 , wherein the processor closes the phase-space trajectory of all radial motional modes.

9. The system of claim 5 , wherein the processor eliminates all amplitude error to enable the pulse sequence to be produced with equal time segments.

10. The system of claim 5 , wherein the processor disentangles the spins and motion of at least four motional modes.

11. The system of claim 6 , wherein processor determines the deviation of a rotation angle for a two-qubit gate.

12. A method comprising:
reconstituting a continuous waveform to a discrete analogue version by a controller;
determining frequencies of a pulse sequence for the discrete analogue version by a processor, wherein the processor uses radial motional mode frequencies, and a desired gate time, wherein the processor generates the pulse sequence by closing phase-space trajectories for the radial motional modes, and wherein the processor disentangles spins and motion, and constrains a Rabi frequency for motional sideband transitions;
configuring one or more sets of micro-electromechanical system (MEMS) mirrors to deliver beams modified by a direct digital synthesizer (DDS) based on the determined frequencies to correct amplitude error; and
illustrating by a display a discrete frequency modulation pulse sequence based on the determined frequencies, wherein the discrete frequency modulation pulse sequence is designed to be a sequence of equal-time segments, wherein each of the equal-time segments have a constant frequency.

13. The method of claim 12 , further comprising:
estimating gross gate error of a plurality of concatenated Molmer-Sorensen gates.

14. The method of claim 12 , wherein the frequency modulation pulse sequence is generated by closing phase space trajectories of one or more radial motional modes.

15. The method of claim 12 , further comprising:
estimating a final-state fidelity of consecutive gates, wherein the estimation considers residual spin-motion entanglement.

16. The method of claim 12 , further comprising:
estimating a final-state fidelity of consecutive gates with a deviation of the Rabi frequency for the motional sideband transitions.

17. The method of claim 12 , further comprising:
applying intentional detuning offset to compensate for amplitude error due to a laser intensity.

Assignees

• Univ Duke

Inventors

• Brown Kenneth R
• Leung Pak Hong
• Huang Shilin
• Zhang Bichen

Classifications

• G02F3/00 Primary

  Optical logic elements; Optical bistable devices · CPC title

• G02F3/026

  based on laser effects · CPC title

• B82Y10/00

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

• G06N10/20

  Models of quantum computing, e.g. quantum circuits or universal quantum computers · CPC title

• B82Y20/00

  Nanooptics, e.g. quantum optics or photonic crystals · CPC title