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1. Suppressing communication errors using quantum-enabled forward error correction

   https://doi.org/10.1116/5.0164396  

   Burenkov, Ivan A.; Annafianto, N. Fajar; Jabir, M. V.; Battou, Abdella; Polyakov, Sergey V. (September 2023, AVS Quantum Science)

   n/a (Ed.)

   Because noise is inherent to all measurements, optical communication requires error identification and correction to protect and recover user data. Yet, error correction, routinely used in classical receivers, has not been applied to receivers that take advantage of quantum measurement. Here, we show how information uniquely available in a quantum measurement can be employed for efficient error correction. Our quantum-enabled forward error correction protocol operates on quadrature phase shift keying (QPSK) and achieves more than 80 dB error suppression compared to the raw symbol error rate and approximately 40 dB improvement of symbol error rates beyond the QPSK classical limit. With a symbol error rate below 10−9 for just 11 photons per bit, this approach enables reliable use of quantum receivers for ultra-low power optical communications. Limiting optical power improves the information capacity of optical links and enables scalable networks with coexisting quantum and classical channels in the same optical fiber. 

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2. Single-photon frequency shifting with a quadrature phase-shift keying modulator

   https://doi.org/10.1038/s41598-020-79511-8  

   Chen, Changchen; Heyes, Jane E.; Shapiro, Jeffrey H.; Wong, Franco N. (December 2021, Scientific Reports)

   Abstract Deterministic frequency manipulation of single photons is an essential tool for quantum communications and quantum networks. We demonstrate a 15.65 GHz frequency shift for classical and nonclassical light using a commercially available quadrature phase-shift keying modulator. The measured spectrum of frequency-shifted single photons indicates a high carrier-to-sideband ratio of 30 dB. We illustrate our frequency shifter’s utility in quantum photonics by performing Hong–Ou–Mandel quantum interference between two photons whose initial frequency spectra overlap only partially, and showing visibility improvement from 62.7 to 89.1% after one of the photons undergoes a corrective frequency shift. 

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3. High Performance Flexible Protocol for Backscattered-Based Neural Implants

   https://doi.org/10.1109/APWC.2019.8870386  

   Arjona, Laura; Rosenthal, James; Smith, Joshua R.; Moritz, Chet T. (September 2019, 2019 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications (APWC))

   This work presents a custom high-performance protocol for bi-directional communication with neural implants, that will eventually enable closed-loop operation. This protocol presents a flexible configuration to communicate to neural implants with different characteristics. It can support different uplink data rates, a variable number of neural channels from 2 to 16, two types of digital signal modulation (Amplitude Shift-Keying, ASK, and Binary Shift-Keying, PSK), and different RF operation frequencies (915MHz being the default). The proposed protocol is implemented in C++ (preferred to Python because it enables fast signal processing algorithms), using GNU-Radio toolkit with custom communication blocks. 

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4. Practical quantum-enhanced receivers for classical communication

   https://doi.org/10.1116/5.0036959  

   Burenkov, I_A; Jabir, M_V; Polyakov, S_V (April 2021, AVS Quantum Science)

   Communication is an integral part of human life. Today, optical pulses are the preferred information carriers for long-distance communication. The exponential growth in data leads to a “capacity crunch” in the underlying physical systems. One of the possible methods to deter the exponential growth of physical resources for communication is to use quantum, rather than classical measurement at the receiver. Quantum measurement improves the energy efficiency of optical communication protocols by enabling discrimination of optical coherent states with the discrimination error rate below the shot-noise limit. In this review article, the authors focus on quantum receivers that can be practically implemented at the current state of technology, first and foremost displacement-based receivers. The authors present the experimentalist view on the progress in quantum-enhanced receivers and discuss their potential. 

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5. Energy and bandwidth efficiency optimization of quantum-enabled optical communication channels

   https://doi.org/10.1038/s41534-022-00573-9  

   Jabir, M. V.; Annafianto, N. Fajar R.; Burenkov, I. A.; Battou, A.; Polyakov, S. V. (May 2022, npj Quantum Information)

   Abstract We present a systematic study of quantum receivers and modulation methods enabling resource efficient quantum-enhanced optical communication. We introduce quantum-inspired modulation schemes that theoretically yield a better resource efficiency than legacy protocols. Experimentally, we demonstrate below the shot-noise limit symbol error rates forM ≤ 16 legacy and quantum-inspired communication alphabets using software-configurable optical communication time-resolving quantum receiver testbed. Further, we experimentally verify that our quantum-inspired modulation schemes boost the accuracy of practical quantum measurements and significantly optimize the combined use of energy and bandwidth for communication alphabets that are longer thanM = 4 symbols. 

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