Optical pulse generation method for creating arbitrary superposition states of qubits in three-level systems

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: 2020-11-17
SUZHOU UNIV +1
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  • Abstract
  • Description
  • Claims
  • Application Information

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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 generation method for creating arbitrary superposition states of qubits in three-level systems
  • Optical pulse generation method for creating arbitrary superposition states of qubits in three-level systems
  • Optical pulse generation method for creating arbitrary superposition states of qubits in three-level systems

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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 a light pulse generation method capable of creating an arbitrary superposition state of qubits in a three-level system. The invariant theory is used to reversely solve the time-dependent Schrodinger equation of the three-level system to construct a set of two-color light capable of generating an arbitrary superposition state of qubits. Field-strength information of the pulse, using an arbitrary wave generator and an acousto-optic modulator, to generate a two-color light pulse, the additional degrees of freedom in the field strength of the two-color light pulse are used to optimize the shape of the pulse for the frequency disturbances present in the system. Harmonic quantities exhibit robustness, and the off-resonance excitation of background ions present in the system is small enough to create arbitrary superposition states of qubits with fidelity in short action times; An arbitrary superposition state of a qubit is generated within the action time, the fidelity is not less than 99.5% in the range of frequency detuning of ±340kHz, and the non-resonant excitation of background ions is not more than 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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Patent Type & Authority Patents(China)
IPC IPC(8): G02F1/35G02F1/33
CPCG02F1/33G02F1/3526
Inventor 延英陈玺李亦超
Owner SUZHOU UNIV
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