Source-device-independent heterodyne-based quantum random number generator at 17 Gbps

For many applications, quantum random number generation should be fast and independent from assumptions on the apparatus. Here, the authors devise and implement an approach which assumes a trusted detector but not a trusted source, and allows random bit generations at ~17 Gbps using off-the-shelf components

Fast and simple qubit-based synchronization for quantum key distribution

We propose Qubit4Sync, a synchronization method for Quantum Key Distribution (QKD) setups, based on the same qubits exchanged during the protocol and without requiring additional hardware other than the one necessary to prepare and measure the quantum states. Our approach introduces a new cross-correlation algorithm achieving the lowest computational complexity, to our knowledge, for high channel losses. We tested the robustness of our scheme in a real QKD implementation

Unbounded randomness from uncharacterized sources

Randomness is a central feature of quantum mechanics and an invaluable resource for both classical and quantum technologies. Commonly, in Device-Independent and Semi-Device-Independent scenarios, randomness is certified using projective measurements and the amount of certified randomness is bounded by the dimension of the measured quantum system. In this work, we propose a new Source-Device-Independent protocol, based on Positive Operator Valued Measurement (POVM), which can arbitrarily increase the number of certified bits for any fixed dimension. A tight lower-bound on the quantum conditional min-entropy is derived using only the POVM structure and the experimental expectation values, taking into account the quantum side-information. For symmetrical POVM measurements on the Bloch sphere we have derived closed-form analytical bounds. Finally, we experimentally demonstrate our method with a compact and simple photonic setup that employs polarization-encoded qubits and POVM up to 6 outcomes.Comment: 9 pages, 6 figure

Stable, low-error and calibration-free polarization encoder for free-space quantum communication

Polarization-encoded free-space Quantum Communication requires a quantum state source featuring fast polarization modulation, long-term stability and a low intrinsic error rate. Here we present a source based on a Sagnac interferometer and composed of polarization maintaining fibers, a fiber polarization beam splitter and an electro-optic phase modulator. The system generates predetermined polarization states with a fixed reference frame in free-space that does not require calibration neither at the transmitter nor at the receiver. In this way we achieve long-term stability and low error rates. A proof-of-concept experiment is also reported, demonstrating a Quantum Bit Error Rate lower than 0.2% for several hours without any active recalibration of the devices.Comment: 6 pages, 2 figure

IKKepsilon involvement in Tax-mediated activation of INF pathway

HTLV-1 Tax de-regulates several cellular signaling pathways leading to cell transformation by altering gene expression, intracellular protein distribution and cell proliferation. Tax-1 induces persistent activation of several transcriptional factors and signal transduction pathways, including NF-\u3baB and CREB/ATF. It is known that Tax-1 constitutively activates TAK1 (transforming growth factor-\u3b2-activated kinase 1) and modifies the interferon (INF) regulatory signals by controlling the expression of INF transcription factors 3 (INF3) and INF4. We have recently reported that HTLV-1 and HTLV-2 Tax proteins interact with TAK1-binding protein 2 (TAB2) of the NF-\u3baB pathway and that both Tax proteins transactivate NF-\u3baB promoters [1]. TAB2 functions as an adaptor protein to recruit TAK1 to TRAF2 (TNF-\u3b1 receptor-associated factor) in TNF-\u3b1 signaling pathways. In the present study we have investigated Tax-1 and Tax-2 role in modifying INF and NF-\u3baB activation through the recruitment of IKKepsilon, an I\u3baB kinase homologue involved in NF-\u3baB and INF3 signaling pathways. By co-immunoprecipitation experiments, we have found that both IKKepsilon and Tax-1, but not Tax-2, are present in protein complexes in transfected cells. IKKepsilon and Tax-1 or Tax-2 role in the activation of INF responsive elements or NF-\u3baB containing promoters have been analyzed after transfecting the protein genes in 293T cells and measuring the effect by luciferase assay. Co-expression of Tax-1 and IKKepsilon resulted in an increased IRF activation mediated by IKKepsilon. Interaction of IKKepsilon with Tax-1 and Tax-2 and their possible effects in the de-regulation of the IRF3 pathways will be discussed

All-fiber self-compensating polarization encoder for Quantum Key Distribution

Quantum Key Distribution (QKD) allows distant parties to exchange cryptographic keys with unconditional security by encoding information on the degrees of freedom of photons. Polarization encoding has been extensively used in QKD implementations along free-space, optical fiber and satellite-based links. However, the polarization encoders used in such implementations are unstable, expensive, complex and can even exhibit side-channels that undermine the security of the implemented protocol. Here we propose a self-compensating polarization encoder based on a Lithium Niobate phase modulator inside a Sagnac interferometer and implement it using only standard telecommunication commercial off-the-shelves components (COTS). Our polarization encoder combines a simple design and high stability reaching an intrinsic quantum bit error rate as low as 0.2%. Since realization is possible from the 800 nm to the 1550 nm band by using COTS, our polarization modulator is a promising solution for free-space, fiber and satellite-based QKD.Comment: REVTeX, 5 pages, 4 figure

Postselection-loophole-free Bell violation with genuine time-bin entanglement

Entanglement is an invaluable resource for fundamental tests of physics and the implementation of quantum information protocols such as device-independent secure communications. In particular, time-bin entanglement is widely exploited to reach these purposes both in free-space and optical fiber propagation, due to the robustness and simplicity of its implementation. However, all existing realizations of time-bin entanglement suffer from an intrinsic postselection loophole, which undermines their usefulness. Here, we report the first experimental violation of Bell's inequality with "genuine" time-bin entanglement, free of the postselection loophole. We introduced a novel function of the interferometers at the two measurement stations, that operate as fast synchronized optical switches. This scheme allowed to obtain a postselection-loophole-free Bell violation of more than nine standard deviations. Since our scheme is fully implementable using standard fiber-based components and is compatible with modern integrated photonics, our results pave the way for the distribution of genuine time-bin entanglement over long distances.Comment: RevTe

Unbounded randomness from uncharacterized sources

Randomness is a central feature of quantum mechanics and an invaluable resource for both classical and quantum technologies. Commonly, in Device-Independent and Semi-Device-Independent scenarios, randomness is certified using projective measurements, and its amount is bounded by the quantum system’s dimension. Here, we propose a Source-Device-Independent protocol, based on Positive Operator Valued Measurement (POVM), which can arbitrarily increase the number of certified bits for any fixed dimension. Additionally, the proposed protocol doesn’t require an initial seed and active basis switching, simplifying its experimental implementation and increasing the generation rates. A tight lower-bound on the quantum conditional min-entropy is derived using only the POVM structure and the experimental expectation values, taking into account the quantum side-information. For symmetric POVM on the Bloch sphere, we derive closed-form analytical bounds. Finally, we experimentally demonstrate our method with a compact and simple photonic setup that employs polarization-encoded qubits and POVM up to 6 outcomes

Semi-Device-Independent Heterodyne-based Quantum Random Number Generator

Randomness is a fundamental feature of quantum mechanics, which is an invaluable resource for both classical and quantum technologies. Practical quantum random number generators (QRNG) usually need to trust their devices, but their security can be jeopardized in case of imperfections or malicious external actions. In this work, we present a robust implementation of a Semi-Device-Independent QRNG that guarantees both security and fast generation rates. The system works in a prepare and measure scenario where measurement and source are untrusted, but a bound on the energy of the prepared states is assumed. Our implementation exploits heterodyne detection, which offers increased generation rate and improved long-term stability compared to alternative measurement strategies. In particular, due to the tomographic properties of heterodyne measurement, we can compensate for fast phase fluctuations via post-processing, avoiding complex active phase stabilization systems. As a result, our scheme combines high security and speed with a simple setup featuring only commercial-off-the-shelf components, making it an attractive solution in many practical scenarios

Semi-device independent randomness from d-outcome continuous-variable detection

Recently, semi-device independent protocols have attracted increasing attention, guaranteeing security with few hypotheses and experimental simplicity. In this paper, we demonstrate a many-outcomes scheme with the binary phase-shift keying (BPSK) for a semi-device independent protocol based on the energy assumption. We show in theory that the number of certified random bits of the d-outcomes system outperforms the standard scheme (binary-outcomes). Furthermore, we compare the results of two well-known measurement schemes, homodyne and heterodyne detection. Lastly, taking into account the experimental imperfections, we discuss the experimental feasibility of the d-outcome design