Practical source of single photons

Benjamin Heinrich

Steven Trpkovski, Lloyd C. L. Hollenberg, Steven Prawer

The nanodiamond technology has developed the first packaged, single-photon source that operates at room temperature and in well-lit environments, where an ideal single-photon source produces one photon per pulse. These sources are key components for building quantum information systems that can implement quantum-key distribution (QKD) for ultrasecure communications. The optically active color centers in diamond have been found to exhibit attractive optical properties through the nitrogen-vacancy (N-V) center emission ranging 600 to 750 nm, and that have realized the practical sources of single-photon emission. Photo statistics has to be determined to measure the performance of a single-photon source, which can be measured by the autocorrelation function g2 (0) using Hanbury-Brown and Twiss interferometer. The results showed that the SPS 1.01 demonstrates stable single-photon performance without requirement of recalibration.

Jie Zhang, Bao-Wen Xu, Lan Zhou +2 more

Abstract A single-photon qudit encoded in more than one degree of freedom (DOF) can effectively enlarge a single photon’s capacity and has great potential for applications in future high-capacity quantum communication fields. During the photon transmission in practical noisy channels, photon qudits may suffer from photon transmission loss, which largely limits their application. In this paper, we propose a practical noiseless linear amplification (NLA) protocol for protecting the single-photon qudit encoded in polarization and double-longitudinal momentum DOFs. This NLA adopts the imperfect entangled state generated from a practical spontaneous parametric down-conversion (SPDC) source as the auxiliary state and can be realized under current experimental conditions. After performing the NLA protocol, the fidelity of the target single-photon qudit can be increased and the encoded information in all DOFs can be well preserved. We show the adoption of the imperfect entangled state generated from SPDC source is superior to that of the imperfect single-photon state from a practical heralded single-photon source. Our NLA protocol has application potential in current and future quantum communications.

Stefania Castelletto, Ivo Pietro Degiovanni, Michael J. Ware +1 more

Many quantum computation and communication schemes require, or would significantly benefit from, true sources of single photon on-demand (SPOD). Unfortunately, such sources do not exist. It is becoming increasingly clear that coupling photons out of a SPOD source will be a limiting factor in many SPOD implementations. In particular, coupling these source outputs into optical fibers (usually single mode fibers) is often the preferred method for handling this light. We investigate the practical limits to this coupling as relates to parametric downconversion, an important starting point for many SPOD schemes. We also explored whether it is possible to optimize the engineering of the downconversion sources to improve on this coupling. We present our latest results in this area.

Matthew T. Rakher