Scheme for generation of three-photon entangled W state assisted by cross-Kerr nonlinearity and quantum dot

Abstract

We represent an optical scheme using cross-Kerr nonlinearities (XKNLs) and quantum dot (QD) within a single-sided optical cavity (QD-cavity system) to generate three-photon entangled W state containing entanglement against loss of one photon of them. To generate W state (three-photon) with robust entanglement against loss of one photon, we utilize effects of optical nonlinearities in XKNLs (as quantum controlled operations) and QD-cavity system (as a parity operation) with linearly optical devices. In our scheme, the nonlinear (XKNL) gate consists of weak XKNLs, quantum bus beams, and photon-number-resolving measurement to realize controlled-unitary gate between two photons while another nonlinear (QD) gate employs interactions of photons and an electron of QD confined within a single-sided optical cavity for implementation of parity gate. Subsequently, for the efficiency and experimental feasibility of our scheme generating W state, we analyze the immunity of the controlled-unitary gate using XKNLs against decoherence effect and reliable performance of parity gate using QD-cavity system.

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

“…Rather, for the experimental realization, to improve the conditions (tendencies: strong coupling strength and small side-leakage) is more advantageous than to maintain the values of parameters fixed in the small range, in practice. Therefore, we can conclude that high efficiency and performance (according to the values of AoF) can be acquired by increase in the coupling strength, and also, with decrease in the side-leakage rate under the vacuum noise, N(ω), for operation of the QD-dipole and leaky modes, S(ω) (sideband leakage and absorption) 51,54,[64][65][66] . Also, our optical Fredkin gate is utilizing the interactions of QD-cavity systems (QD1 and QD2) with high efficiency and performance when to increase the coupling strength, g >> (κ, γ), and decrease the side-leakage rate, κ s << κ.…”

“…c where the reflectances and phase shifts are |r h (ω)| = |r 0 (ω)|≈1 and ϕ rh (ω)≈0, ϕ r0 (ω)≈π for g/κ = 2.4, and γ/κ = 0.1 with κ s → 0 and ω = ω c (frequencies: external field = cavity mode) 2,4,[11][12][13]15,[41][42][43][44][45][46][47][48][49][50][51][52][53][54] . According to the reflection operator, Eq.…”

“…5, of QD-cavity system. www.nature.com/scientificreports www.nature.com/scientificreports/ In practice, for the high efficiency and reliable performance of the QD-cavity system, which can induce the interaction an input photon and an confined electron inside cavity, the affections of the vacuum noise, N(ω), of the QD-dipole and leaky modes, S(ω) (sideband leakage and absorption) should be quantified 51,54,[64][65][66] . For the reflection coefficient, R( ) ω , with the noise, N(ω), and leakage, S(ω), coefficients, a solution of the Heisenberg equation of motion for a cavity field operator, â, a dipole operator, σ̂−, of X − , and the input-output relations 67 , is given by:ˆˆω…”

“…Because our gate employs the interactions between a photon (control qubit) and two electrons (target qubits) inside the QD-cavity systems (QD within a single-sided optical cavity), the long coherence time of target qubits (swapped electron spin states) can be achieved from the storage of quantum information in QD, for the reliable performance of the Fredkin gate. Subsequently, for the reliable Fredkin gate, we demonstrate the high efficiency and reliable performance of the interaction of photon-electron in QD under the vacuum noise in the QD-dipole operation, and leaky modes (sideband leakage and absorption) in the cavity mode through our analysis 51,54,[64][65][66] . Consequently, the proposed Fredkin gate using QD-cavity systems has the feasibility and the reliable performance to experimentally realize the controlled-swap gate under the vacuum noise and leaky modes (sideband leakage and absorption).…”

“…To obtain scheme for quantum information processing with the reliable performance, the most important task is to maintain the coherence of quantum state when to operate the procedure of multi-qubit controlled operations. In quantum dot (QD)-cavity system, which consists of an injected excess electron and a confined negatively charged exciton (X − ) in optical cavity 2,4,[11][12][13]15,[41][42][43][44][45][46][47][48][49][50][51][52][53][54] , quantum information can be well stored for a long electron-spin coherence time (T 2 e~μ s) 43,45,46,[55][56][57] and a limited spin relaxation period (T 1 e~m s) 42,50,58,59 against the influence (decoherence effect) of environment. Therefore, several diverse quantum information processing schemes have been designed between photons and electrons in the QD-cavity system, as quantum controlled gates 21,[24][25][26]30,31,[47][48][49]52,60 , quantum communications [10][11][12]…”