skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.


Title: Suppressing communication errors using quantum-enabled forward error correction
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.  more » « less
Award ID(s):
1927674
PAR ID:
10481060
Author(s) / Creator(s):
; ; ; ;
Publisher / Repository:
AVS co-published with AIP
Date Published:
Journal Name:
AVS Quantum Science
Volume:
5
Issue:
3
ISSN:
2639-0213
Page Range / eLocation ID:
031403
Subject(s) / Keyword(s):
quantum-enabled error correction, forward error correction, bayesian probabilities
Format(s):
Medium: X Size: n/a Other: n/a
Size(s):
n/a
Sponsoring Org:
National Science Foundation
More Like this
  1. 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. 
    more » « less
  2. In this paper we theoretically and experimentally demonstrate a novel adaptation of independent component analysis (ICA) for compensation of both cross-polarization and inter-symbol interference in a direct-detection link using Stokes vector modulation (SVM). SVM systems suffer from multiple simultaneous impairments that can be difficult to resolve with conventional optical channel DSP techniques. The proposed method is based on a six-dimensional adaptation of ICA that simultaneously de-rotates the SVM constellation, corrects distortion of constellation shape, and mitigates inter-symbol interference (ISI) at high symbol rates. Experimental results at 7.5 Gb/s and 15Gb/s show that the newly developed ICA-based equalizer achieves power penalties below ∼1 dB, compared to the ideal theoretical bit-error rate (BER) curves. At 30-Gb/s, where ISI is more severe, ICA still enables polarization de-rotation and BER < 10−5before error correction. 
    more » « less
  3. Quantum technologies are maturing by the day and their near-term applications are now of great interest. Deep-space optical communication involves transmission over the pure-state classical-quantum channel. For optimal detection, a joint measurement on all output qubits is required in general. Since this is hard to realize, current (sub-optimal) schemes perform symbol-by-symbol detection followed by classical post-processing. In this paper we focus on a recently proposed belief propagation algorithm by Renes that passes qubit messages on the factor graph of a classical error-correcting code. More importantly, it only involves single-qubit Pauli measurements during the process. For an example 5-bit code, we analyze the involved density matrices and calculate the error probabilities on this channel. Then we numerically compute the optimal joint detection limit using the Yuen-Kennedy-Lax conditions and demonstrate that the calculated error probabilities for this algorithm appear to achieve this limit. This represents a first step towards achieveing quantum communication advantage. We verify our analysis using Monte-Carlo simulations in practice. 
    more » « less
  4. We implement the cyclic quantum receiver based on the theoretical proposal of Roy Bondurant and demonstrate experimentally below the shot-noise limit (SNL) discrimination of quadrature phase-shift keying signals (PSK). We also experimentally test the receiver generalized for longer communication alphabet lengths and coherent frequency shift keying (CFSK) encoding. Using off-the-shelf components, we obtain state discrimination error rates that are 3 dB and 4.6 dB below the SNLs of ideal classical receivers for quadrature PSK and CFSK encodings, respectively. The receiver unconditionally surpasses the SNL for M=8 PSK and CFSK. This receiver can be used for the simple and robust practical implementation of quantum-enhanced optical communication. 
    more » « less
  5. Iftekharuddin, Khan M.; Awwal, Abdul A.; Márquez, Andrés; Diaz-Ramirez, Victor H. (Ed.)
    One of the biggest challenges of free-space optical (FSO) communication is the wave-front aberration due to atmospheric turbulence. In FSO links the wave-front distortion manifests as a significant drop in received power, beam wander, information loss, and scintillation effects. The performance of FSO communication system is degraded significantly by the atmospheric turbulence effects. Fortunately, the adaptive optics system offers potential to mitigate the performance degradation, which is relevant for quantum communication applications as well. In our FSO experiment, we perform the transmission of 6.25 GBd QPSK signal over an FSO link without and with adaptive optics, operating at 1550nm. We emulate the atmospheric aberration in our indoor experimental setup by applying random Kolmogorov phase screens on spatial light modulators (SLMs). We demonstrate significant improvements in the power-collected, signal-to-noise-ratio (SNR), and bit-error-rate (BER) performance due to the application of adaptive optics. 
    more » « less