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Optical pulse generating method capable of creating three-energy-level system quantum bit random superposition state

A quantum bit, optical pulse technology, applied in the field of optical pulse, can solve the problems of long pulse action time and poor robustness

Active Publication Date: 2018-08-17
SUZHOU UNIV +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] The technical problem solved by the present invention is: the pulse action time is too long and the robustness is poor; the present invention seeks a method for generating a group of two-color light pulses, the two-color light pulses are composed of two pulses with equal duration and different amplitudes, frequencies and phases. Composed of pulses, the two act on a three-level quantum system composed of two qubit energy levels and an excited state energy level at the same time, and the quantum system can be manipulated to generate any superposition state of qubits from the initial state |1> where θ a ∈[0,π], Under certain conditions, the generated light pulses have the following characteristics:

Method used

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  • Optical pulse generating method capable of creating three-energy-level system quantum bit random superposition state
  • Optical pulse generating method capable of creating three-energy-level system quantum bit random superposition state
  • Optical pulse generating method capable of creating three-energy-level system quantum bit random superposition state

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Embodiment 1

[0033] An optical pulse generation method that can create arbitrary superposition states of qubits in a three-level system, according to the initial state |1> and the target state of the system where θ a In the range [0, π], Take the value in the range of [0, 2π], use the adiabatic shortcut technology based on the Lewis-Riesenfeld invariant theory to reversely solve the time-dependent Schrödinger equation of the three-level system to obtain the amplitude and phase of the two optical pulses, and input the amplitude and phase The arbitrary wave generator generates a radio signal with the same amplitude and phase as the optical pulse, and uses this radio signal to drive the acousto-optic modulator in the continuous laser optical path to obtain +1 or -1 deflected output light, generating a set of two-color optical pulses;

[0034] Where: the driving frequency of the acousto-optic modulator is f aom , the laser frequency in the continuous laser path is f laser , the qubit is c...

Embodiment 2

[0053] The optical pulse generation method that can create any superposition state of the three-level system qubit based on the first embodiment, all a in the formula (4) n The values ​​are all zero. at this time:

[0054]

[0055] Based on this γ(t) and β(t) shown in formula (5), the Rabi frequency of the light pulse generated by formulas (2) and (3) can be found in the attached figure 2 , where the solid line is Ω p , the dotted line is Ω s , the pulse action time is 4μs, the start and end values ​​of the Rabi frequency are not equal to zero, and the maximum instantaneous Rabi frequency does not exceed 0.5MHz.

[0056] attached image 3 is the evolution of the quantum state |ψ(t)> with time during the interaction between the pulse and the detuned quantum system. At the initial moment, the quantum state is in the |1> state; at the end of the pulse, that is, t=4μs, the probability of the quantum state in both |0> and |1> is 50%, which is the same as the target state ...

Embodiment 3

[0060] The optical pulse generation method that can create any superposition state of qubits in the three-level system based on the first embodiment, a in formula (4) n All even and odd terms of satisfy the following two conditions respectively:

[0061] a 1 +3a 3 +5a 5 +7a 7 = 0,

[0062] a 2 +2a 4 +3a 6 +4a 8 =-0.5.

[0063] Then the Rabi frequency of the two light pulses at the initial and final moments is zero, that is, Ω p,s (t=0,tf)=0. By any a that satisfies these two relations n Substituting the value into (4), the constructed light pulse can manipulate the quantum system to create the target state |ψ target >, here in the simplest case a 2 =-0.5, a 1.3.4.5.6.7.8 =0 as an example to illustrate the shape of the light pulse and its working performance.

[0064] attached Figure 4 , is the Rabi frequency of the two-color light pulse in this embodiment, and the values ​​at the initial and termination moments are both zero, avoiding the existence of multiple...

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Abstract

The invention discloses an optical pulse generating method capable of creating the three-energy-level system quantum bit random superposition state. An invariant theory is adopted to reversely solve atime-dependent Schrodinger equation of a three-energy-level system, field intensity information of a group of polychromatic optical pulses capable of generating the quantum bit random superposition state is constructed, an arbitrary wave generator and an acoustic and optical modulator are utilized to generate the polychromatic optical pulses, the extra degree of freedom in the polychromatic optical pulse field intensity is utilized to optimize the shape of the pulses, so that the pulses show robustness to the frequency detuning amount existing in the system, and have small-enough non-resonance excitation of background ions existing in the system, and thus the quantum bit random superposition state is created with the fidelity within a short acting time. By means of the optical pulse generating method, the optical pulses can generate the quantum bit random superposition state within the acting time of 4 microseconds, the fidelity within the frequency detuning amount range of + / -340 kHzis not lower than 99.5%, and the non-resonance excitation of the background ions does not exceed 2%.

Description

technical field [0001] The invention belongs to the field of quantum computing, and in particular relates to an optical pulse capable of manipulating a quantum system to generate any superposition state of qubits. Background technique [0002] Quantum computing is an important branch of quantum information processing. It has an unmatched computing speed of classical computing algorithms in problems such as factorization of large prime numbers, global search, and biomolecular simulation. Initializing a qubit into an arbitrary superposition state with high fidelity in a short time using pulses of light is the first step towards unlocking quantum computing. However, some interference factors inevitably exist in the physical system, such as frequency detuning, optical field intensity fluctuations, optical field phase fluctuations, non-resonant excitation and other interferences. How to generate light pulses so that they are robust to these disturbances when manipulating qubits,...

Claims

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Application Information

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IPC IPC(8): G02F1/35G02F1/33
CPCG02F1/33G02F1/3526
Inventor 延英陈玺李亦超
Owner SUZHOU UNIV
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