Quantum key distribution (QKD) is the first commercial application of the second quantum revolution. Although QKD systems have already been developed and implemented all around the world, some open challenges are limiting the overall deployment of this technology (limited key rate, limited link distance, etc.). By improving the current QKD protocols, it is possible to increase the final secret key generation rate. In this work, we compare 1-decoy with 2-decoy methods in BB84 protocol over an underwater optical fiber link connecting Malta to Italy, showing that 2-decoy can achieve more than twice the key rate of 1-decoy method.
A QKD link established between Sicily (Italy) and Malta has been utilized to test the performances of a fast-gated InGaAs single photon detector, achieving a fourteen times higher key rate than using a commercial detector.
In the context of emerging quantum technologies, this work marks an important progress towards practical quantum optical systems in the continuous variable regime. It shows the feasibility of experiments where non-Gaussian state generation entirely relies on plug-and-play components from guided-wave optics technologies. This strategy is successfully demonstrated with the heralded preparation of low amplitude Schrödinger cat states via single-photon subtraction from a squeezed vacuum. All stages of the experiment are based on off-the-shelf fiber components. This leads to a stable, compact, and easily re-configurable realization, fully compatible with existing fiber networks and, more in general, with future out-of-the-laboratory applications.
This work marks an important progress towards practical quantum optical technologies in the continuous variable regime, as it shows the feasibility of experiments where non-Gaussian state generation entirely relies on plug-&-play components from guided-wave optics technologies. This strategy is demonstrated experimentally with the heralded preparation of low amplitude Schrödinger cat states based on single-photon subtraction from a squeezed vacuum. All stages of the experiment are based on off-the-shelf fiber components. This leads to a stable, compact, and easily re-configurable realization, fully compatible with existing fibre networks and, more in general, with future out-of-the-laboratory applications.
This work demonstrates the capabilities of an entangled photon-pair source at telecom wavelengths, based on a photonic integrated Si 3 N 4 microresonator, with monolithically integrated piezoelectric frequency tuning. Previously, frequency tuning of photon-pairs generated by microresonators has only been demonstrated using thermal control. However, these have limited actuation bandwidth, and are not compatible with cryogenic environments. Here, the frequency-tunable photon-pair generation capabilities of a Si 3 N 4 microresonator with a monolithically integrated aluminium nitride layer are shown. In addition, fast-frequency locking of the microresonator to an external laser is demonstrated, with a resulting locking bandwidth many times higher than achieved with previous thermal locking schemes. These abilities add to the existing 'photonic toolbox' available when using such integrated microresonators as photon-pair sources, and will have direct application in future schemes which interface such sources with quantum memories based on e.g. trapped-ion or rare-earth ion schemes.
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