High-fidelity stimulated Raman adiabatic passage analog in optimum three-waveguide system

High-fidelity resonant tunneling passage in three-waveguide system

“…When light is injected initially into waveguide L, the resonant tunneling passage resembles the optimized STIRAP in the three-waveguide system. [23] The analyses are described as follows. First, the STIRAP in a waveguide system is realized by using counterintuitive tunneling rate distributions, here, the envelope function A R (z) dominates over A L (z) at the early stage while A L (z) dominates in the end, these two envelope functions correspond to counterintuitive tunneling rates as shown in Figs.…”

“…[22] The optimized schemes for quantum systems are robust against small variations in experimental parameters and hence some schemes have been used to design the waveguide coupler. For example, to improve the tunneling efficiency of waveguides systems, STI-RAP scheme, [5] DDP technique, [23] STA scheme, [24][25][26] and non-Hermitian shortcut to AP scheme [27] are extended to the designing of waveguides couplers. It is noted that the opti-mized techniques mentioned above are all adiabatic.…”

“…[5] No matter whether the amplitudes and widths of the tunneling rates or the distance between two peak tunneling rates changes, the nonadiabatic tunneling exists and the fidelity of the STIRAP is near the benchmark 10 −4 of QIP. [23] Then non-Hermitian shortcut to AP scheme, an optimization scheme based on STIRAP, introduces a non-Hermitian term to cancel nonadiabatic tunneling. The fidelity of AP is increased, and tunneling distance is shortened.…”

“…Although the fidelity is further improved, the length of coupler is still long. [23] The STA technique, based on transitionless quantum driving algorithm, introduces an unfeasible relative phase and has been exploited to shorten the length of waveguides coupler. [25] The total length of coupler is about 1/6 of the one designed by traditional schemes, however the disadvantage of STA scheme is that the channel width changes continuously along the coupler, hence such a structure is difficult for practical implementations and stays mainly in the stage of theoretical research.…”

“…[32,33] The STA technique and the STIRAP technique have been used to design single-qubit gates, such as Not-and Hadamard gates. [23,34] Owing to the robustness of the resonant tunneling passage, a train of N-stage three-waveguide systems has the potential to design a high-fidelity Hadamard gate, which is one of the fundamental gates in QIP.…”