Fast optical source for quantum key distribution based on semiconductor optical amplifiers

Abstract

Abstract:A novel integrated optical source capable of emitting faint pulses with different polarization states and with different intensity levels at 100 MHz has been developed. The source relies on a single laser diode followed by four semiconductor optical amplifiers and thin film polarizers, connected through a fiber network. The use of a single laser ensures high level of indistinguishability in time and spectrum of the pulses for the four different polarizations and three different levels of intensity. The applicability of the source is demonstrated in the lab through a free space quantum key distribution experiment which makes use of the decoy state BB84 protocol. We achieved a lower bound secure key rate of the order of 3.64 Mbps and a quantum bit error ratio as low as 1.14 × 10 −2 while the lower bound secure key rate became 187 bps for an equivalent attenuation of 35 dB. To our knowledge, this is the fastest polarization encoded QKD system which has been reported so far. The performance, reduced size, low power consumption and the fact that the components used can be space qualified make the source particularly suitable for secure satellite communication.

Quantum estimation of the Schwarzschild spacetime parameters of the Earth

“…We consider that the wave-packets will be peaked at frequencies Ω 1 = Ω 2 = 400THz with widths of σ = 1MHz. These parameters correspond to the current state of the art in space-based experiments [34]. Gbit exchange regimes of N = 10 10 are achieved with the aim of implementing future QKD protocols [35,36].…”

Satellite‐Based Quantum Steering under the Influence of Spacetime Curvature of the Earth

“…Since the height of current GPS (Global Position System) satellites is km. For this distance the influence of relativistic disturbance of the spacetime curvature on quantum steerability cannot be ignored for the quantum information tasks at current level technology . Hence, in this work the plotting range of the satellite height will be constrained to geostationary satellites height.…”

Experimental comparison between one-decoy and two-decoy implementations of the Bennett-Brassard 1984 quantum cryptography protocol

“…The decoy-state method so far has been implemented for the free-space quantum channel [15,16] and for the fiber-optic quantum channel [17][18][19] for specific average photon numbers per pulse for the signal (μ) and the decoy (ν) states. Although the optimal values of μ and ν can be calculated [20,21], there has not been an experimental study which investigated whether the theoretical optimum conditions match well with those of the experimental ones.…”