Photonic scheme of discrete quantum Fourier transform for quantum algorithms via quantum dots

Abstract

We propose an optical scheme of discrete quantum Fourier transform (DQFT) via ancillary systems using quantum dots (QDs) confined in single-sided cavities (QD-cavity systems). In our DQFT scheme, the main component is a controlled-rotation k (CRk) gate, which utilizes the interactions between photons and QDs, consisting of two QD-cavity systems. Since the proposed CRk gate can be experimentally implemented with high efficiency and reliable performance, the scalability of multi-qubit DQFT scheme can also be realized through the simple composition of the proposed CRk gates via the QD-cavity systems. Subsequently, in order to demonstrate the performance of the CRk gate, we analyze the interaction between a photon and a QD-cavity system, and then indicate the condition to be efficient CRk gate with feasibility under vacuum noise and sideband leakage.

Optical Fredkin gate assisted by quantum dot within optical cavity under vacuum noise and sideband leakage

“…Quantum controlled operations play critical roles in quantum information processing schemes, such as quantum computation [1][2][3][4][5][6][7] and quantum communication [8][9][10][11][12][13][14][15] , to accomplish a reliable performance with high efficiency. One of the universal quantum operations is controlled-NOT (CNOT) gate, which can perform the spin-flipping of a target qubit with regard to the state of a control qubit, and has been researched theoretically and experimentally [16][17][18][19][20][21][22] .…”

Encoding scheme using quantum dots for single logical qubit information onto four-photon decoherence-free states

“…Quantum phenomena can produce various quantum information processing schemes, such as quantum communications [1][2][3][4] , quantum computation [5][6][7][8][9][10][11] , quantum controlled operations [12][13][14][15] , and quantum entanglement [16][17][18][19][20][21][22] , in theory and practice. And if these schemes are experimentally realized, the mitigation of the decoherence effect will be a pivotal issue for the reliable quantum information processing.…”

“…In our scheme, the QD-cavity (single-sided) systems, which can interact between a flying photon (photonic qubit) and an excess electron (spin qubit) of the QD, are crucial elements for the realization of single logical qubit information encoded arbitrary quantum information and the generation of four-photon decoherence-free states. Thus, for a reliable performance of the QD-cavity systems interactions, we quantify the experimental conditions of a QD-cavity system under vacuum noise in QD-dipole operation, and leaky modes (sideband leakage and absorption) in cavity mode 11,20,22,[54][55][56][57][58] via analysis of the Heisenberg equation of motion 57 . Consequently, we demonstrate that the encoding scheme for single logical qubit information onto four-photon decoherence-free states is robust against collective decoherence and experimental feasibility.…”

“…In this section, we introduce the concept of a quantum dot (QD) within a cavity (QD-cavity system) 11,20,22,47,58,[62][63][64][65][66][67][68][69] , which can induce the interaction of a photon and a singly charged QD (a negatively charged exciton:X − ). For the coherence of quantum systems in quantum information processing schemes, the systems of micropillar cavities have been widely utilized to construct quantum controlled gates 11,20,22,47,58,[62][63][64][65][66][67][68][69] . Additionally, quantum information in the QD-cavity system can be effectively isolated from the environment for a long electron-spin coherence time ( T e 2 ~ µs) [70][71][72][73][74][75] and a limited spin relaxation period ( T e 1 ~ ms) [76][77][78][79] .…”

“…1a, and the spin selection rule, Fig. 1b, in the QD 11,20,22,47,58,[62][63][64][65][66][67][68][69] are presented with |↑� ≡ |+1/2�,|↓� ≡ |−1/2� (the spin states of the excess electron), and |⇑� ≡ |+3/2�, |⇓� ≡ |−3/2� (heavy-hole spin states). The single-sided cavity consists of two GaAs/Al(Ga)As distributed Bragg reflectors, DBR: the bottom DBR is partially reflective and the top DBR, 100% reflective, and a transverse index guide for the three-dimensional confinement of light.…”