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Quantum Electronics and Laser Science Conference

Free-space daylight single-photon communications over 1.6 km

W. T. Buttler, Richard Hughes, S. K. Lamoreaux, George L. Morgan, J. E. Nordholt, Charles G. Peterson

Published Jan 1, 2000• 0 citations
OpenAlex

Abstract

Summary form only given. The QKD transmitter, Alice, consists of three diode lasers (a timing laser and two data lasers: one data laser transmits vertical polarized photons, while the other transmits 45 degree polarized photons, two matching interference filters (IF), two optical attenuators, two linear polarizers, two non-polarizing beamsplitters, a 27/spl times/ beam expander, and a single-photon detector (SPD). The two data-laser (dimpulse) wavelengths are temperature controlled and constrained by the IF to 773/spl plusmn/0.5 nm, while the timing-laser (bright-pulse) transmitted wavelength is temperature controlled to /spl sim/768 nm. The data-lasers are configured to emit dim-light pulses of /spl sim/1 ns duration, and the SPD measures the average photon number per transmitted dim-pulse. This system uses the B92 QKD protocol, but could be easily adapted to the BB84 QKD protocol. The transmitter incorporates no active polarization switching.

Related papers

Free space quantum key distribution in daylight

Richard Hughes, J. E. Nordholt, George L. Morgan +1 more

Summary form only given. The Los Alamos free-space quantum key distribution (QKD) system operates at a 1-MHz clock rate. On each clock cycle a /spl sim/1-ns "bright timing pulse" is emitted from an array of /spl sim/1550-nm lasers at the transmitter ("Alice"). After a /spl sim/100 ns delay one of four temperature-controlled "data" diode lasers emits a /spl sim/1-ns, 772-nm optical pulse that is attenuated to the single-photon level. We present results from operations over multi-kilometer atmospheric ranges. The spectral, spatial and temporal filtering allow practical secret bit rates even in full daylight. We also present a study of a satellite-to-ground QKD system, and an analysis of the expected secret bit rate.

Quantum Electronics and Laser Science Conference•Jun 25, 2003•3 citations

QKD using polarization encoding with active measurement basis selection

Alexander Duplinskiy, Vasily E. Ustimchik, A. A. Kanapin +1 more

We report a proof-of-principle quantum key distribution experiment using a one-way optical scheme with polarization encoding implementing the BB84 protocol. LiNbO 3 phase modulators are used for generating polarization states for Alice and active basis selection for Bob. This allows the former to use a single laser source, while the latter needs only two single-photon detectors. The presented optical scheme is simple and consists of standard fiber components. Calibration algorithm for three polarization controllers used in the scheme has been developed. The experiment was carried with 10 MHz repetition frequency laser pulses over a distance of 50 km of standard telecom optical fiber.

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The goal of cryptography is to encode data in such a way that no one can decode it unless they are the intended recipient. With the emergence of quantum computing, classical cryptography is not reliable enough to protect sensitive information. Nevertheless, there are alternatives. Quantum Key Distribution (QKD) is a method to secure communication based on the laws of quantum physics. Due to being impossible to measure the quantum state of a system without disturbing it, QKD provides a way to communicate between two parties while being, in theory, immune to eavesdropping. In this work, a free-space high-speed QKD setup is proposed, with the objective of implementing the polarization three-state one-decoy variant of the BB84 protocol. An assessment of the best type of laser diode to use for free-space QKD is made between several options. The system’s performance was assessed, incorporating a quantitative analysis of system losses and an estimation of the number of photons traversing the quantum channel. The system achieved a Quantum Bit Error Rate (QBER) of 1.58% for the Z basis and 1.46% for the X basis, for an average reception of two photons per pulse. Preliminary QBER measurements were also undertaken in the context of Quantum Keyless Private Communication protocols, focusing on the average number of photons per pulse.

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Low cost, short range, free space quantum key distribution.

David Lowndes

We present a Quantum Key Distribution system comprising a hand held transmitter device (Alice) and a fixed terminal (Bob). The devices are highly asymmetrical with as much functionality as possible placed into the Bob terminal (a 4u 19in. rack) which is much less restricted on its size. The small size (80x50x10mm) and relatively low complexity will allow the hand held Alice to be cheaply mass produced and therefore widely available. A potential use for this technology would be as a method to allow the general public to benefit from a wider metropolitan or national QKD network by establishing key with trusted network nodes. The Alice device optics comprise 4 pulsed 300um LEDs behind polarizers to produce the photon states for the BB84 protocol. Light from the LEDs is combined and spatially filtered using a single mode fibre, the output of which is collimated by a lens at the optical output of the device. The device is currently controlled via USB by a PC or mobile phone. The Bob terminal is split into two modules; broadly categorized as “optical” and “processing”. The optical module contains beam splitters for state discrimination and photon detection. The processing module contains a PC, wireless router, time-tagging electronics and power supply. The modular approach allows for a flexible platform for different QKD experiments, for example change of wavelength or protocol would involve switching out only the optical module. This work forms part of the Quantum Communications hub and was carried out with EPSRC funding (Quantum Communications Hub, grant no. EP/M013472/1).

•Jan 1, 2016•0 citations

BB84 quantum key distribution transmitter utilising broadband sources and a narrow spectral filter

Yoann Noblet, Ross J. Donaldson

The secure nature of Quantum Key Distribution (QKD) protocols makes it necessary to ensure that the single photon sources are indistinguishable. Any spectral, temporal or spatial discrepancy between the sources would lead to a breach in the security proofs of the QKD protocols. Traditional, weak-coherent pulse implementations of polarization-based QKD protocols have relied on identical photon sources obtained through tight temperature control and spectral filtering. However, it can be challenging to keep the temperature of the sources stable over time, particularly in a real-world setting, meaning photon sources can become distinguishable. In this work, we present an experimental demonstration of a QKD system capable of achieving spectral indistinguishability, over a 10°C range, using a combination of broadband sources, super-luminescent light emitting diodes (SLEDs), along with a narrow band-pass filter. The temperature stability could be useful in a satellite implementation, where there may be temperature gradients over the payload, particularly on a CubeSat.

Optics Express•Apr 13, 2023•6 citations

A short wavelength GigaHertz clocked fiber-optic quantum key distribution system

Karen J. Gordon, Verónica Fernández, Paul D. Townsend +1 more

A quantum key distribution (QKD) system has been developed, using a standard telecommunications optical fiber, which is capable of operating at clock rates of greater than 1 GHz. The QKD system implements a polarization encoded version of the B92 protocol. The system employs vertical-cavity surface-emitting lasers with emission wavelengths of 850 nm as weak coherent light sources, and silicon single photon avalanche diodes as the single photon detectors. A distributed feedback laser of emission wavelength 1.3 /spl mu/m, and a linear gain germanium avalanche photodiode was used to optically synchronize individual photons over the standard telecommunications fiber. The QKD system exhibited a quantum bit error rate (QBER) of 1.4%, and an estimated net bit rate (NBR) greater than 100 000 bits/sup -1/ for a 4.2-km transmission range. For a 10-km fiber range, a QBER of 2.1%, and an estimated NBR of greater than 7000 bits/sup -1/ was achieved.

arXiv:quant-ph/0605222•IEEE Journal of Quantum Electronics•Jun 30, 2004•158 citations
Summary form only given. The QKD transmitter, Alice, consists of three diode lasers (a timing laser and two data lasers: one data laser transmits vertical polarized photons, while the other transmits 45 degree polarized photons, two matching interference filters (IF), two optical attenuators, two linear polarizers, two non-polarizing beamsplitters, a 27/spl times/ beam expander, and a single-photon detector (SPD). The two data-laser (dimpulse) wavelengths are temperature controlled and constrained by the IF to 773/spl plusmn/0.5 nm, while the timing-laser (bright-pulse) transmitted wavelength is temperature controlled to /spl sim/768 nm. The data-lasers are configured to emit dim-light pulses of /spl sim/1 ns duration, and the SPD measures the average photon number per transmitted dim-pulse. This system uses the B92 QKD protocol, but could be easily adapted to the BB84 QKD protocol. The transmitter incorporates no active polarization switching.
Summary form only given. The Los Alamos free-space quantum key distribution (QKD) system operates at a 1-MHz clock rate. On each clock cycle a /spl sim/1-ns "bright timing pulse" is emitted from an array of /spl sim/1550-nm lasers at the transmitter ("Alice"). After a /spl sim/100 ns delay one of four temperature-controlled "data" diode lasers emits a /spl sim/1-ns, 772-nm optical pulse that is attenuated to the single-photon level. We present results from operations over multi-kilometer atmospheric ranges. The spectral, spatial and temporal filtering allow practical secret bit rates even in full daylight. We also present a study of a satellite-to-ground QKD system, and an analysis of the expected secret bit rate.
We report a proof-of-principle quantum key distribution experiment using a one-way optical scheme with polarization encoding implementing the BB84 protocol. LiNbO 3 phase modulators are used for generating polarization states for Alice and active basis selection for Bob. This allows the former to use a single laser source, while the latter needs only two single-photon detectors. The presented optical scheme is simple and consists of standard fiber components. Calibration algorithm for three polarization controllers used in the scheme has been developed. The experiment was carried with 10 MHz repetition frequency laser pulses over a distance of 50 km of standard telecom optical fiber.
The goal of cryptography is to encode data in such a way that no one can decode it unless they are the intended recipient. With the emergence of quantum computing, classical cryptography is not reliable enough to protect sensitive information. Nevertheless, there are alternatives. Quantum Key Distribution (QKD) is a method to secure communication based on the laws of quantum physics. Due to being impossible to measure the quantum state of a system without disturbing it, QKD provides a way to communicate between two parties while being, in theory, immune to eavesdropping. In this work, a free-space high-speed QKD setup is proposed, with the objective of implementing the polarization three-state one-decoy variant of the BB84 protocol. An assessment of the best type of laser diode to use for free-space QKD is made between several options. The system’s performance was assessed, incorporating a quantitative analysis of system losses and an estimation of the number of photons traversing the quantum channel. The system achieved a Quantum Bit Error Rate (QBER) of 1.58% for the Z basis and 1.46% for the X basis, for an average reception of two photons per pulse. Preliminary QBER measurements were also undertaken in the context of Quantum Keyless Private Communication protocols, focusing on the average number of photons per pulse.
We present a Quantum Key Distribution system comprising a hand held transmitter device (Alice) and a fixed terminal (Bob). The devices are highly asymmetrical with as much functionality as possible placed into the Bob terminal (a 4u 19in. rack) which is much less restricted on its size. The small size (80x50x10mm) and relatively low complexity will allow the hand held Alice to be cheaply mass produced and therefore widely available. A potential use for this technology would be as a method to allow the general public to benefit from a wider metropolitan or national QKD network by establishing key with trusted network nodes. The Alice device optics comprise 4 pulsed 300um LEDs behind polarizers to produce the photon states for the BB84 protocol. Light from the LEDs is combined and spatially filtered using a single mode fibre, the output of which is collimated by a lens at the optical output of the device. The device is currently controlled via USB by a PC or mobile phone. The Bob terminal is split into two modules; broadly categorized as “optical” and “processing”. The optical module contains beam splitters for state discrimination and photon detection. The processing module contains a PC, wireless router, time-tagging electronics and power supply. The modular approach allows for a flexible platform for different QKD experiments, for example change of wavelength or protocol would involve switching out only the optical module. This work forms part of the Quantum Communications hub and was carried out with EPSRC funding (Quantum Communications Hub, grant no. EP/M013472/1).
The secure nature of Quantum Key Distribution (QKD) protocols makes it necessary to ensure that the single photon sources are indistinguishable. Any spectral, temporal or spatial discrepancy between the sources would lead to a breach in the security proofs of the QKD protocols. Traditional, weak-coherent pulse implementations of polarization-based QKD protocols have relied on identical photon sources obtained through tight temperature control and spectral filtering. However, it can be challenging to keep the temperature of the sources stable over time, particularly in a real-world setting, meaning photon sources can become distinguishable. In this work, we present an experimental demonstration of a QKD system capable of achieving spectral indistinguishability, over a 10°C range, using a combination of broadband sources, super-luminescent light emitting diodes (SLEDs), along with a narrow band-pass filter. The temperature stability could be useful in a satellite implementation, where there may be temperature gradients over the payload, particularly on a CubeSat.
A quantum key distribution (QKD) system has been developed, using a standard telecommunications optical fiber, which is capable of operating at clock rates of greater than 1 GHz. The QKD system implements a polarization encoded version of the B92 protocol. The system employs vertical-cavity surface-emitting lasers with emission wavelengths of 850 nm as weak coherent light sources, and silicon single photon avalanche diodes as the single photon detectors. A distributed feedback laser of emission wavelength 1.3 /spl mu/m, and a linear gain germanium avalanche photodiode was used to optically synchronize individual photons over the standard telecommunications fiber. The QKD system exhibited a quantum bit error rate (QBER) of 1.4%, and an estimated net bit rate (NBR) greater than 100 000 bits/sup -1/ for a 4.2-km transmission range. For a 10-km fiber range, a QBER of 2.1%, and an estimated NBR of greater than 7000 bits/sup -1/ was achieved.