Complete elimination of information leakage in continuous-variable quantum communication channels

Jacobsen, Christian S.; Madsen, Lars S.; Usenko, Vladyslav C.; Filip, Radim; Andersen, Ulrik L.

doi:10.1038/s41534-018-0084-0

Cited by 28 publications

(41 citation statements)

References 52 publications

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“…Our method is focused on maximizing mutual information (not on eliminating cross-correlations) and leads to optimal improvement of the key rate. Note, that our method can be advantageously combined with the protocol, in which the Holevo information, maximally accessible to Eve, is minimized [48]. In this scenario by proper multiplexing and elimination of crosstalk higher key rate can be achieved at low post-processing efficiencies, while not increasing the information leakage.…”

Section: Resultsmentioning

confidence: 93%

Frequency multiplexed entanglement for continuous-variable quantum key distribution

Kovalenko¹,

Ra²,

Chen³

et al. 2021

Preprint

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Quantum key distribution with continuous variables already uses advantageous high-speed single-mode homodyne detection with low electronic noise at room temperature. Together with continuous-variable information encoding to nonclassical states, the distance for secure key transmission through lossy channels can approach 300 km in current optical fibers. Such protocols tolerate higher channel noise and also limited data processing efficiency compared to coherent-state protocols. The secret key rate can be further increased by increasing the system clock rates, and, further, by a suitable frequency-mode-multiplexing of optical transmission channels. However, the multiplexed modes couple together in the source or any other part of the protocol. Therefore, multiplexed communication will experience crosstalk and the gain can be minuscule. Advantageously, homodyne detectors allow solving this crosstalk problem by proper data processing. It is a potential advantage over protocols with single-photon detectors, which do not enable similar data processing techniques. We demonstrate the positive outcome of this methodology on the experimentally characterized frequency-multiplexed entangled source of femtosecond optical pulses with natural crosstalk between eight entangled pairs of modes. As the main result, we predict almost 15-fold higher secret key rate. This experimental test and analysis of frequency-multiplexed entanglement source opens the way for the field implementation of high-capacity quantum key distribution with continuous variables.

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Section: Resultsmentioning

confidence: 93%

Frequency multiplexed entanglement for continuous-variable quantum key distribution

Kovalenko¹,

Ra²,

Chen³

et al. 2021

Preprint

Self Cite

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“…Furthermore, in the case when untrusted additive Gaussian channel noise can be ruled out by trusted device calibration, the trusted parties can group the transmitted data according to estimated stable transmittance windows corresponding to non-fluctuating noiseless channels [50], apply shot-noise-limited modulation of squeezed signal states hence preventing an unauthorized party from gaining any information on the key [58] and improve the resulting key rate by channel multiplexing [59][60][61]. In the presence of channel noise the protocol optimization along with the post-selection techniques [19,62] and Gaussian error correction aimed at overcoming low-frequency additive Gaussian noise [63], can significantly improve the performance of Gaussian CV QKD protocols in atmospheric links, enabling efficient and robust free-space quantum key distribution, fully applicable in daylight conditions.…”

Section: Discussionmentioning

confidence: 99%

Squeezing-enhanced quantum key distribution over atmospheric channels

2020

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We propose the Gaussian continuous-variable quantum key distribution using squeezed states in the composite channels including atmospheric propagation with transmittance fluctuations. We show that adjustments of signal modulation and use of optimal feasible squeezing can be sufficient to significantly overcome the coherent-state protocol and drastically improve the performance of quantum key distribution in atmospheric channels, also in the presence of additional attenuating and noisy channels. Furthermore, we consider examples of atmospheric links of different lengths, and show that optimization of both squeezing and modulation is crucial for reduction of protocol downtime and increase of secure atmospheric channel distance. Our results demonstrate unexpected advantage of fragile squeezed states of light in the free-space quantum key distribution applicable in daylight and stable against atmospheric turbulence.Quantum key distribution (QKD) [1-5] is one of the major practical applications of quantum information theory, which provides trusted parties (Alice and Bob) with the methods (protocols) for provably secure distribution of secret cryptographic keys so that security of the key can be verified using fundamental principles of quantum physics. One of the main requirements of QKD is the availability of a dedicated quantum channel capable of transmitting coherent quantum signals between the sending and receiving stations. In the case of fiber-optical channels, being the typical media for QKD implementations, this means a dedicated optical fiber, possibly with co-existing classical or quantum signals. However, the dedicated fiber-optical infrastructure can be unavailable, e.g., in the case of movable stations, necessity of quick channel deployment or in hostile environments. Moreover, the extra-long-distance inter-continental quantum communication over satellites relies on the free-space channels [6]. Therefore, the free-space channels are an important physical medium for QKD implementations.The main issue faced by the discrete-variable (DV) QKD protocols, based on single-photon states or weak coherent pulses and the direct photon counting, is the sensitivity of the detectors to the background light, which adds noise to the measured data. This renders standard DV QKD protocols practically unusable in the daylight conditions unless spectral filtering is applied, which adds unwanted additional loss and complexity to the set-up. At the same time, applicability and efficiency are crucial for QKD as they directly affect the secret communication, based on the quantum-secure keys. Alternatively, continuous-variable (CV) QKD protocols [7-10], based on the multiphoton coherent [11][12][13][14][15] or squeezed states [16] and homodyne quadrature detection using off-the-shelf equipment, can overcome this limitation. Indeed, a homodyne detector, which matches a signal to a narrow-band local oscillator (LO) beam, being the phase reference for the measurement, can intrinsically filter out the background radiation and make CV Q...

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“…This fundamental quantum property of squeezed states has been the engine of numerous quantum sensing experiments, such as the quantum-enhanced measurements of gravitational waves [4] and vibrational modes of molecules [5,6], and recent quantum computing models including Gaussian boson sampling [7,8] and measurement-based quantum computing [9][10][11]. Furthermore, the use of squeezed states (compared to coherent states) improves the performance of continuous variable quantum key distribution systems by increasing the tolerance to optical loss, excess noise and imperfect error correction [12][13][14], effectively allowing longer transmission distances or improved security.…”

Section: Introductionmentioning

confidence: 99%

40 km Fiber Transmission of Squeezed Light Measured with a Real Local Oscillator

Suleiman¹,

Nielsen²,

Guo³

et al. 2022

Preprint

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We demonstrate the generation, 40 km fiber transmission, and homodyne detection of single-mode squeezed states of light at 1550 nm using real-time phase control of a locally generated local oscillator, often called a "real local oscillator" or "local local oscillator". The system was able to stably measure up to around 3.7 dB of noise suppression with a phase noise uncertainty of around 2.5 • , using only standard telecom-compatible components and a field-programmable gate array (FPGA). The compactness, low degree of complexity and efficacy of the implemented scheme makes it a relevant candidate for long distance quantum communication in future photonic quantum networks.

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Complete elimination of information leakage in continuous-variable quantum communication channels

Cited by 28 publications

References 52 publications

Frequency multiplexed entanglement for continuous-variable quantum key distribution

Frequency multiplexed entanglement for continuous-variable quantum key distribution

Squeezing-enhanced quantum key distribution over atmospheric channels

40 km Fiber Transmission of Squeezed Light Measured with a Real Local Oscillator

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