Simultaneous Quantum State Measurement using Array Detection

Andrew M. C. Dawes, M. Beck

M. Beck, Christophe Dorrer, Ian A. Walmsley

Andrew M. C. Dawes, M. Beck

We have simultaneously measured the quantum states of two different spatial modes of the same optical beam by performing quantum-state tomography with an array detector. Both modes are well described by coherent states, but the projection of the signal onto the local oscillator mode contains a mean of 0.09 photons, while a more complicated mode has a mean of 4.3 photons. This demonstrates that for this particular mode the effective detection efficiency when using array detection is over 40 times greater than when using single detectors.

Wenyuan Hao, Y. W. Jin, Huan Fei Wen +10 more

Abstract The efficient detection of digital signals plays a vital role in optimizing the reliability and stability of communication systems. This paper demonstrates a method to optically measure digital signals based on solid‐state quantum spin. The digital signals are non‐intrusively characterized by taking advantage of the optical readability of the spin states of the nitrogen‐vacancy (NV) centers array. Meanwhile, the resonance frequencies of optically detected magnetic resonance (ODMR) spectra are spatially encoded by means of an external magnetic field gradient, thereby realizing the simultaneous acquisition of three‐channel digital signals. Over a continuous detection bandwidth of 258 MHz, digital signals can be detected with a time resolution of 3 ms and a minimum signal strength of 0 dBm. Afterward, the ability of this system to capture digital signals is further substantiated by measuring signals in other channels. This proposal is competent for the simultaneous analysis of multi‐channel signals in real‐time and provides a valuable reference for radio spectrum monitoring, and signal intelligence reconnaissance.

Giacomo Mauro D’Ariano

Alexandre M. Zagoskin, R. D. Wilson, M. J. Everitt +5 more

We propose a method of resolving a spatially coherent signal, which contains on average just a single photon, against the background of local noise at the same frequency. The method is based on detecting the signal simultaneously in several points more than a wavelength apart through the entangling interaction of the incoming photon with the quantum metamaterial sensor array. The interaction produces the spatially correlated quantum state of the sensor array, characterised by a collective observable (e.g., total magnetic moment), which is read out using a quantum nondemolition measurement. We show that the effects of local noise (e.g., fluctuations affecting the elements of the array) are suppressed relative to the signal from the spatially coherent field of the incoming photon as , where N is the number of array elements. The realisation of this approach in the microwave range would be especially useful and is within the reach of current experimental techniques.