Fault-Tolerant Information Processing with Quantum Weak Measurement

Abstract

Noise is an important factor that influences the reliability of information acquisition, transmission, processing, and storage. In order to suppress the inevitable noise effects, a fault-tolerant information processing approach via quantum weak measurement is proposed, where pairwise orthogonal postselected measurement bases with various tiny angles and optimal compositions of measured results are chosen as a decoding rule. The signal to be protected can be retrieved with a minimal distortion after having been transmitted through a noisy channel. Demonstrated by typical examples of encoding signal on two-level superposition state or Einstein-Podolsky-Rossen state transmitted through random telegraph noise and decoherence noises channel, the mean squared error distortion may be close to $0$ and the fault-tolerant capability could reach $1$ with finite quantum resources. To verify the availability of the proposed approach, classic coherent light and quantum coherent state are used for encoding information in the experiment. Potentially, the proposed approach may provide a solution for suppressing noise effects in long-distance quantum communication, high-sensitivity quantum sensing, and accurate quantum computation.

Figures (1)

• Figure 1: Theoretical description and experimental implementation of the FTIP approach. (a) Theoretical model. An arbitrary signal to be protected is encoded onto the initial quantum states, then transmitted through a noisy channel, and finally decoded via postselected measurement bases. (b) Schematic diagram of four pairwise orthogonal measurement bases. $\varepsilon_{1,2}$ are symmetric with respect to a systematical axis $(\varepsilon_1+\varepsilon_2)/2$, and the angular between $\ket{\phi_1}$ and $\ket{\phi_2}$ is $2\varepsilon$. (c) Schematic diagram of the FTIP approach encoding information on EPR state. (d) Experiment setup. The implementation of using quantum coherent state is enclosed by blue boxes, including the attenuation of coherent light via variable optical attenuator and homodyne detection on the signal light. The abbreviations in the figure are as following, VOA: variable optical attenuator, P: polarizer, FC: fiber collimator, PM: phase modulator, AWG: arbitrary waveform generator, PC: polarization controller, BS: beam splitter, HWP: half-wave plate, QWP: quarter-wave plate. SL: signal light, LO: local oscillator light, OH: free space passive optical hybrid, BPD: balanced photodetector. (e) The retrieved results when using quantum coherent state. (f) The retrieved results when using classical coherent light.