Optical pulse design method for high-fidelity manipulation over ensemble qubits

Patent metadata

Field	Value
Publication number	US-12387124-B2
Application number	US-202117783373-A
Country	US
Kind code	B2
Filing date	Feb 25, 2021
Priority date	Nov 6, 2020
Publication date	Aug 12, 2025
Grant date	Aug 12, 2025

Abstract

The present invention discloses an optical pulse design method for high-fidelity manipulation over ensemble qubits, so that fast and efficient two-color optical pulses that have high robustness against frequency detuning and a laser intensity fluctuation are constructed by using an inverse engineering method based on a Lewis-Riesenfeld invariant, and using a perturbation theory and a concept of a system error sensitivity. The pulses can be applied in an inhomogeneously broadened three-level system to create an arbitrary superposition state of ensemble qubits with a high fidelity. During action of the pulse, quantum manipulation has stronger robustness against instantaneous changes or spatial nonuniform distribution of a laser intensity. The robustness can increase a signal-to-noise ratio of a detected signal and reduce experimental difficulties. In addition, the time that the qubits are in an excited state is significantly reduced, which can greatly reduce a decoherence effect of the qubits and ensure high-fidelity manipulation.

First claim

What is claimed is:

1. An optical pulse design method for high-fidelity manipulation over ensemble qubits, comprising:
solving a time-dependent Schrödinger equation of a three-level system inversely based on a Lewis-Riesenfeld invariant theory;
taking a laser intensity fluctuation as a perturbation;
using a perturbation theory to calculate a deviation of a quantum manipulation fidelity caused by the laser intensity fluctuation, the deviation being represented by a system error sensitivity;
designing amplitudes and phases of two optical pulses when an initial state and a target state of the three-level system are known based on a condition that the system error sensitivity is approximately zero;
inputting the amplitudes and the phases into an arbitrary waveform generator to generate radio signals with the same amplitude and phase as the two optical pulses;
using the radio signals to drive an acousto-optic modulator in a continuous laser optical path to obtain +1-order or −1-order deflection output light to generate a set of two-color optical pulses, the set of two-color optical pulses being normally incident to a three-level quantum system medium; and
interacting the set of two-color optical pulses and the three-level quantum system medium to generate an arbitrary superposition state of qubits,
wherein the initial state |1 and the target state |ψtarget =cos θ a |1 +sin θ a e iφ a |0 of the system are provided, wherein θ a and φ a are two angles, and θ a is in the range of [0, π], representing distribution of the population at two levels: |0 and |1 ; a value of φ a is in the range of [0, 2π], representing a relative phase between the qubit levels |0 and |1 ;
wherein a driving frequency of the acousto-optic modulator is f aom , a laser frequency in the continuous laser optical path is f laser , the qubits are represented by two levels: |0 and |1 , a frequency difference therebetween is f 0-1 , an optical transition frequency between the level |1 and a level |e is v p , an optical transition frequency between the level |0 and the level |e is v s , a frequency of a radio signal that drives the acousto-optic modulator to generate optical pulses acting on transition of |1 to |e is f p , a frequency of a radio signal that drives the acousto-optic modulator to generate optical pulses acting on transition of |0 to |e is f s , the two meet f p =f aom , and f s =f aom +f 0-1 , f laser +f p =v p ; f laser +f s =v s ; phases of the two radio signals are denoted as: φ p and φ s , and amplitudes are denoted as E p and E s ;
then the following are met: φ p =0, φ s =φ a , E p and E s change with time, and are determined by the following relation formula:

E

p
,
s

=

-

ℏ

μ

p
,
s

·
C
·

{

Ω

p
,
s

,

Ω

p
,
s

>
0

e

i
⁢
π

⁢

❘
"\[LeftBracketingBar]"

Ω

p
,
s

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,

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p
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<
0

,

(
1
)

wherein μ p,s is a transition dipole moment of optical transition of |1 to |e and |0 to |e ; Ω p,s is a Rabi frequency of the two optical pulses; C is a coefficient of conversion from the Rabi frequency Ω p,s of the optical pulses to the amplitude E p,s of the radio signals, and is determined by an experimental system; the Rabi frequency Ω p,s depending on a time t is denoted as the following formula:
Ω p =2[{dot over (β)} cot γ( t )sin β( t )+{dot over (γ)} cos β( t )]  (2),

Ω s =2[{dot over (β)} cot γ( t )cos β( t )−γ sin β( t )]  (3),

wherein β(t) and γ(t) are functions that depend on time; {dot over (β)} and {dot over (γ)} are differentials of the functions β(t) and γ(t) with respect to the time;
a laser intensity fluctuation is taken as a perturbation, and a quantum perturbation theory is used to calculate influence of a

Assignees

• Univ Soochow

Inventors

• Yan Ying
• Mo Ze
• Chen Tianfeng
• Wan Lin
• Wang Jiayi

Classifications

• G02F1/11 Primary

  based on acousto-optical elements, e.g. using variable diffraction by sound or like mechanical waves (acousto-optical deflection G02F1/33) · CPC title

• G01J1/4257

  applied to monitoring the characteristics of a beam, e.g. laser beam, headlamp beam (monitoring arrangements for lasers in general H01S3/0014) · CPC title

• G06N10/40 Primary

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

• G01J2001/4238

  Pulsed light · CPC title

• G06N10/00 Primary

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