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

Abstract

We propose a deterministic Fredkin gate which can accomplish controlled-swap operation between three-qubit states. The proposed Fredkin gate consists of a photonic system (single photon) and quantum dots (QDs) confined in single-sided cavities (two electron spin states). In our scheme, the control qubit is the polarization state of the single photon, and two electron spin states in QDs play the role of target qubits (swapped states by control qubit). The interaction between a photon and an electron of QD within the cavity (QD-cavity system) significantly affects the performance of Fredkin gate. Thus, through the analysis of the QD-cavity system under vacuum noise and sideband leakage, we demonstrate that reliable interaction and performance of the QD-cavity system with photonic state (photon) can be acquired in our scheme. Consequently, the Fredkin gate proposed in this paper can be experimentally implemented with high feasibility and efficiency.

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

“…of the reflected photon, according to the hot or cold cavity. Therefore, the analysis of the interaction between a photon and an electron spin state in the QD is required to quantify the efficiency and reliability of the QD-cavity system under vacuum noise N(ω) , for the operation of the QD-dipole, and leaky modes S(ω) (sideband leakage and absorption) 11,20,22,[54][55][56]84,85 . To figure out the affections of the vacuum noise N(ω) and leaky modes S(ω) in the QD-cavity system, we can calculate the quantum Langevin equations of a cavity field operator â , a dipole operator σ − of X − , and the input-output relations with vacuum noise N(ω) and leaky modes S(ω) from the Jaynes-Cummings Hamiltonian H JC 11,20,22,[54][55][56]84,85 , as follows:…”

“…2.3 , the critical components are the QD-cavity systems, which can perform the reflection operators, [ ] and [ ], to induce differences in the reflectances and phase shifts of the reflected photon, according to the hot or cold cavity. Therefore, the analysis of the interaction between a photon and an electron spin state in the QD is required to quantify the efficiency and reliability of the QD-cavity system under vacuum noise , for the operation of the QD-dipole, and leaky modes (sideband leakage and absorption) 11 , 20 , 22 , 54 – 56 , 84 , 85 . To figure out the affections of the vacuum noise and leaky modes in the QD-cavity system, we can calculate the quantum Langevin equations of a cavity field operator , a dipole operator of , and the input–output relations with vacuum noise and leaky modes from the Jaynes-Cummings Hamiltonian 11 , 20 , 22 , 54 – 56 , 84 , 85 , as follows: where ( ) is the input (output) field operator from the leaky modes, due to sideband leakage and absorption in the cavity mode, and is the vacuum noise operator for of .…”

“…In Sect. 2.2 , we assumed the approximation of weak excitation with the ground state in the QD, (no saturation), for the steady state, 11 , 20 , 22 , 54 – 56 , 84 , 85 . Therefore, we can calculate the noise ( ) and leakage ( ) coefficients of the hot (cold) cavity, with , as follows: where the reflection coefficient ( ) is expressed in Eq.…”

“…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.…”

Procedure via cross-Kerr nonlinearities for encoding single logical qubit information onto four-photon decoherence-free states

“…The influence of decoherence (nonunitary process) is one of the most significant obstacles hindering the reliable performance of various quantum information processing schemes, such as quantum communication [1][2][3][4][5][6], quantum entanglement [7][8][9][10][11][12], and quantum computation [13][14][15][16][17][18]. Therefore, the influence of decoherence should be reduced via active processes (quantum error corrections [19][20][21] and decoupling and feedback controls [22][23][24][25]) or passive processes (decoherence-free subspaces [26][27][28][29][30]).…”