Field trial of a three-state quantum key distribution scheme in the Florence metropolitan area

Abstract

In-field demonstrations in real-world scenarios boost the development of a rising technology towards its integration in existing infrastructures. Although quantum key distribution (QKD) devices are already adopted outside the laboratories, current field implementations still suffer from high costs and low performances, preventing this emerging technology from a large-scale deployment in telecommunication networks. Here we present a simple, practical and efficient QKD scheme with finite-key analysis, performed over a 21 dB-losses fiber link installed in the metropolitan area of Florence (Italy). Coexistence of quantum and weak classical communication is also demonstrated by transmitting an optical synchronization signal through the same fiber link.

Cross-encoded quantum key distribution exploiting time-bin and polarization states with qubit-based synchronization

“…The temporal synchronization is achieved using the Qubit4Sync algorithm [21]. This implies that the two parties do not need a shared clock reference such as a pulsed laser [4,5,19]. Alice's clock is recovered by Bob only using the time-of-arrival of qubits while the absolute time is recovered by sending an initial public string encoded in the first 10 6 states of the QKD transmission.…”

“…QKD is characterized by a consolidated composable security framework [1,2] and by rapid and continuous technical advancements [3]. In fact, several QKD field trials are being performed to demonstrate the real-world applicability of this technology [4][5][6][7] and several start-ups and university spin-offs are being created to intercept the growing market demands.…”

“…To make QKD performance independent of the polarization fluctuations of the optical fiber, time-bin encoding was introduced as it exploits time-of-arrival of photons and the relative phase between time bins [18]. This encoding has been employed in many QKD field trials in deployed fibers [4,5], as well as in the record-setting 421 km fiber QKD link demonstration of the BB84 protocol [19]. However, time-bin has the disadvantage of requiring phase stabilization of the interferometers which encode and decode the superposition of time bins [20].…”

A Supersymmetry and Quantum Cryptosystem with Path Integral Approach in Biology

“…Nowadays, a topological quantum cryptography is the most secure cryptography concept with the highest impact on computer security, business, and society, but it is rarely used in biology. Experimental quantum cryptography narrows the gap and it approaches the implementation of theoretical knowledge outside the laboratories, e.g., by the investigation of quantum key distribution with finite decoy states [13,14].…”

Common-clock very long baseline interferometry using a coherent optical fiber link

“…Common-clock very long baseline interferometry using a coherent optical fiber link The transmission of optical signals with an ultrastable, well-known frequency using optical fibers dates back to the '90s, when specific techniques were first developed to cancel the effect of mechanical fiber noise on the optical phase [1,2]. This redesigned the experimental practice in fundamental frequency metrology, allowing the comparison of distant atomic clocks at their ultimate accuracy over increasingly longer distances [3][4][5][6][7][8][9], and other unprecedented experiments in high-resolution atomic [10][11][12] and molecular physics [13][14][15], relativistic geodesy [9], quantum communication [16,17], and even seismology, for what concerns the detection of underwater earthquakes in seas and oceans [18]. The need of distributing frequency reference signals between distant sites without deterioration arose even before in radio astronomy and geodesy, for deep-space communication and tracking [19] and the synchronization of radio telescope arrays.…”