Quantum reading: the experimental set-up (original) (raw)

Experimental quantum reading with photon counting

Science Advances, 2021

The final goal of quantum hypothesis testing is to achieve quantum advantage over all possible classical strategies. In the protocol of quantum reading, this is achieved for information retrieval from an optical memory, whose generic cell stores a bit of information in two possible lossy channels. We show, theoretically and experimentally, that quantum advantage is obtained by practical photon-counting measurements combined with a simple maximum-likelihood decision. In particular, we show that this receiver combined with an entangled two-mode squeezed vacuum source is able to outperform any strategy based on statistical mixtures of coherent states for the same mean number of input photons. Our experimental findings demonstrate that quantum entanglement and simple optics are able to enhance the readout of digital data, paving the way to real applications of quantum reading and with potential applications for any other model that is based on the binary discrimination of bosonic loss.

A Method for the Measurement of Photons Number and Squeezing Parameter in a Quantum Cavity

ISRN Optics, 2013

Measurement of photons number in a quantum cavity is very difficult and the photons number is changed after each measurement. Recently, many efforts have been done for the nondemolition measurement methods. Haroche et al. succeed in recognizing existence or nonexistence of one photon in a quantum cavity. In this paper, we employ their experimental setup for a quantum nondemolition measurement and pump a coherent state in their quantum cavity. In this case, we could detect more photons in the quantum cavity by a measurement of a displaced Wigner function. It is also shown that the measurement of more than one photon is possible by the Haroche method by measuring just one point of displaced Wigner function. Furthermore, if the cavity field is filled by a superposition of two number states, the average number of photons within the cavity would be measurable. We show that their setup is also suitable to apply for the measurement of the squeezing parameter for the squeezed state of photo...

Binary Quantum Communication using Squeezed Light: Theoretical and Experimental Frame Work

INTERNATIONAL JOURNAL OF COMPUTERS & TECHNOLOGY

The aim of this paper is to develop framework to generate squeezed light for binary quantum communication. Both theoretical and experimental models to generate squeezed state  using optical parametric amplifier (OPO), which is implemented around He-Ne laser, are described in details. The results will be used as a guide line to investigate the performance of squeezed light-based quantum communication over noisy channel and this issue will be presented in accompanying paper [1]. Â

Observation of Quantum Advantage with Squeezed Light for Absorption Measurement

2020

Absorption measurements are routinely used in science and engineering, it is an exceptionally versatile tool for most applications. For absorption measurements using laser beams of light, the sensitivity is theoretically limited by the shot noise due to the fundamental Poisson distribution of photon number in laser radiation. In practice, the shot-noise limit can only be achieved when all other sources of noise are eliminated. Here, we use bright squeezed light to demonstrate direct absorption measurement can be performed with sensitivity beyond the shot-noise limit. We present a practically realizable scheme, where the bright squeezed light is in the continuous-variable regime generated by the four-wave mixing process in an atomic rubidium vapor. This is a direct sub-shot-noise measurement of absorption, and more than 1 dB quantum advantage for the measurement sensitivity is demonstrated at faint absorption levels. A theoretical model that yields excellent agreements with experimen...

Binary Quantum Communication using Squeezed Light: Numerical, Simulation, and Experimental Resuts

INTERNATIONAL JOURNAL OF COMPUTERS & TECHNOLOGY

In this paper, the squeezed quantum state is generated using an optical parametric oscillator via a spontaneous parametric down conversion technique to investigate squeezed states with quantum noise in one quadrature below the standard quantum limit at the expense of the other. The setup involves four main parts: generation of Nd-YAG second harmonic via a ring resonator, squeezed cavity with a nonlinear crystal inside to generate the squeezed state, Pound-Drever-Hall technique to stabilize the laser in the squeezed cavity and balanced homodyne receiver with high efficiency to detect the squeezed state. A comparison in error probability is addressed between the quantum coherent classical and the quantum squeezed non-classical state in the presence of thermal noise and the dissipation. It is found that with extremely low number of photons, the squeezed state is robust against channel noise.