Semi-device independent randomness generation based on quantum state's indistinguishability

Semi-device independent (Semi-DI) quantum random number generators (QRNGs) gained attention for security applications, offering an excellent trade-off between security and generation rate. This paper presents a proof-of-principle time-bin encoding semi-DI QRNG experiments based on a prepare-and-measure scheme. The protocol requires two simple assumptions and a measurable condition: an upper-bound on the prepared pulses' energy. We lower-bound the conditional min-entropy from the energy-bound and the input-output correlation, determining the amount of genuine randomness that can be certified. Moreover, we present a generalized optimization problem for bounding the min-entropy in the case of multiple input and outcomes, in the form of a semidefinite program. The protocol is tested with a simple experimental setup, capable of realizing two configurations for the ternary time-bin encoding scheme. The experimental setup is easy-to-implement and comprises commercially available off-the-shelf components at the telecom wavelength, granting a secure and certifiable entropy source. The combination of ease-of-implementation, scalability, high security level and output-entropy, make our system a promising candidate for commercial QRNGs

Single-photon-based clock analysis and recovery in quantum key distribution

Quantum key distribution is one of the first quantum technologies ready for the market. Current quantum telecommunication systems usually utilize a service channel for synchronizing the transmitter (Alice) and the receiver (Bob). However, the possibility of removing this service channel and exploiting a clock recovery method are intriguing for future implementation, both in fiber and free-space links. In this paper, we investigate criteria to recover the clock in a quantum communication scenario and experimentally demonstrated the possibility of using a quantum-based clock recovery system in a time-bin quantum key distribution protocol. The performance of the clock recovery technique, in terms of quantum bit error rate and secret key rate, is equivalent to using the service channel for clock sharing.</p

QKD field-trial in Padua: a resource-effective implementation with the iPOGNAC encoder

Quantum key distribution (QKD) is one of the most mature among the quantum technologies that allows two remote users to generate secret keys with unconditional security. To increase its adoption, simple, low-cost, and robust systems are necessary, together with demonstrations in real environments. Here, we present a QKD field-trial over optical fibers deployed in the city center of Padua, Italy. Our system exploits two key technologies developed by our group: a low-error, self-stabilized polarization encoder, called iPOGNAC, and a novel synchronization technique, called Qubit4Sync, which allows us to minimize the experimental complexity of our system

4-Dimensional Quantum Key Distribution Protocol over 52-km Deployed Multicore Fibre

We demonstrate a 4-dimensional path-encoded QKD system over a 52-km multi-core fieldinstalled fibre. The 4D-QKD has a 68.5 kbit/s secret key rate, which is 118% higher than the equivalent 2D-QKD over the same link, owing to the higher dimensionality and greater noise resilience

4-Dimensional Quantum Key Distribution Protocol over 52-km Deployed Multicore Fibre

We demonstrate a 4-dimensional path-encoded QKD system over a 52-km multi-core fieldinstalled fibre. The 4D-QKD has a 68.5 kbit/s secret key rate, which is 118% higher than the equivalent 2D-QKD over the same link, owing to the higher dimensionality and greater noise resilience

Full daylight quantum-key-distribution at 1550 nm enabled by integrated silicon photonics

The future envisaged global-scale quantum-communication network will comprise various nodes interconnected via optical fibers or free-space channels, depending on the link distance. The free-space segment of such a network should guarantee certain key requirements, such as daytime operation and the compatibility with the complementary telecom-based fiber infrastructure. In addition, space-to-ground links will require the capability of designing light and compact quantum devices to be placed in orbit. For these reasons, investigating available solutions matching all the above requirements is still necessary. Here we present a full prototype for daylight quantum key distribution at 1550 nm exploiting an integrated silicon-photonics chip as state encoder. We tested our prototype in the urban area of Padua (Italy) over a 145 m-long free-space link, obtaining a quantum bit error rate around 0.5% and an averaged secret key rate of 30 kbps during a whole sunny day (from 11:00 to 20:00). The developed chip represents a cost-effective solution for portable free-space transmitters and a promising resource to design quantum optical payloads for future satellite missions

Qcosone: A chip-based prototype for daylight free-space QKD at telecom wavelength

Here we present a daylight QKD system using silicon photonics. The system exhibits continuous daytime operation, outperforms comparable systems by two orders of magnitude, and represents a promising resource for future satellite mission

Qcosone: A chip-based prototype for daylight free-space QKD at telecom wavelength

Here we present a daylight QKD system using silicon photonics. The system exhibits continuous daytime operation, outperforms comparable systems by two orders of magnitude, and represents a promising resource for future satellite missions

Full daylight quantum-key-distribution at 1550 nm enabled by integrated silicon photonics

Abstract The future envisaged global-scale quantum-communication network will comprise various nodes interconnected via optical fibers or free-space channels, depending on the link distance. The free-space segment of such a network should guarantee certain key requirements, such as daytime operation and the compatibility with the complementary telecom-based fiber infrastructure. In addition, space-to-ground links will require the capability of designing light and compact quantum devices to be placed in orbit. For these reasons, investigating available solutions matching all the above requirements is still necessary. Here we present a full prototype for daylight quantum key distribution at 1550 nm exploiting an integrated silicon-photonics chip as state encoder. We tested our prototype in the urban area of Padua (Italy) over a 145 m-long free-space link, obtaining a quantum bit error rate around 0.5% and an averaged secret key rate of 30 kbps during a whole sunny day (from 11:00 to 20:00). The developed chip represents a cost-effective solution for portable free-space transmitters and a promising resource to design quantum optical payloads for future satellite missions