Random bits, true and unbiased, from atmospheric turbulence

Random numbers represent a fundamental ingredient for numerical simulation, games, informa- tion science and secure communication. Algorithmic and deterministic generators are affected by insufficient information entropy. On the other hand, suitable physical processes manifest intrinsic unpredictability that may be exploited for generating genuine random numbers with an entropy reaching the ideal limit. In this work, we present a method to extract genuine random bits by using the atmospheric turbulence: by sending a laser beam along a 143Km free-space link, we took advantage of the chaotic behavior of air refractive index in the optical propagation. Random numbers are then obtained by converting in digital units the aberrations and distortions of the received laser wave-front. The generated numbers, obtained without any post-processing, pass the most selective randomness tests. The core of our extracting algorithm can be easily generalized for other physical processes

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

Real-Time Source Independent Quantum Random Number Generator with Squeezed States

Random numbers are a fundamental ingredient for many applications including simulation, modelling and cryptography. Sound random numbers should be independent and uniformly distributed. Moreover, for cryptographic applications they should also be unpredictable. We demonstrate a real-time self-testing source independent quantum random number generator (QRNG) that uses squeezed light as source. We generate secure random numbers by measuring the quadratures of the electromagnetic field without making any assumptions on the source; only the detection device is trusted. We use a homodyne detection to alternatively measure the Q and P conjugate quadratures of our source. Using the entropic uncertainty relation, measurements on P allow us to estimate a bound on the min-entropy of Q conditioned on any classical or quantum side information that a malicious eavesdropper may detain. This bound gives the minimum number of secure bits we can extract from the Q measurement. We discuss the performance of different estimators for this bound. We operate this QRNG with a squeezed state and we compare its performance with a QRNG using thermal states. The real-time bit rate was 8.2 kb/s when using the squeezed source and between 5.2-7.2 kb/s when the thermal state source was used.Comment: 11 pages, 9 figure

Quantified Effects of the Laser Seeding Attack in Quantum Key Distribution

Quantum key distribution (QKD) enables private communications with information-theoretic security. To guarantee the practical security of QKD, it is essential that QKD systems are implemented in accordance to theoretical requirements and robust against side-channel attacks. Here we study a prominent attack on QKD transmitters known as the laser seeding attack (LSA). It consists in injecting photons into the laser of the transmitter in an attempt to modify the outgoing light in some way that is beneficial to the eavesdropper. In this work we measure the response of a QKD transmitter to the LSA as a function of the optical power injected, allowing us to quantify the level of optical attenuation required to mitigate the attack. Further, we employ a laser rate equation model to numerically simulate the effects of the LSA on a gain-switched laser. With this model we are able to reproduce previous experimental results, as well as generate new insight into the LSA by examining the effects of the LSA when the QKD transmitter is operated with different laser current driving parameters

A Hybrid Integrated Quantum Key Distribution Transceiver Chip

Quantum photonic technologies, such as quantum key distribution, are already benefiting greatly from the rise of integrated photonics. However, the flexibility in design of these systems is often restricted by the properties of the integration material platforms. Here, we overcome this choice by using hybrid integration of ultra-low-loss silicon nitride waveguides with indium phosphide electro-optic modulators to produce high-performance quantum key distribution transceiver chips. Access to the best properties of both materials allows us to achieve active encoding and decoding of photonic qubits on-chip at GHz speeds and with sub-1% quantum bit error rates over long fibre distances. We demonstrate bidirectional secure bit rates of 1.82 Mbps over 10 dB channel attenuation and positive secure key rates out to 250 km of fibre. The results support the imminent utility of hybrid integration for quantum photonic circuits and the wider field of photonics.Comment: 13 pages, 5 figures, 1 tabl

A modulator-free quantum key distribution transmitter chip

Quantum key distribution (QKD) has convincingly been proven compatible with real life applications. Its wide-scale deployment in optical networks will benefit from an optical platform that allows miniature devices capable of encoding the necessarily complex signals at high rates and with low power consumption. While photonic integration is the ideal route toward miniaturisation, an efficient route to high-speed encoding of the quantum phase states on chip is still missing. Consequently, current devices rely on bulky and high power demanding phase modulation elements which hinder the sought-after scalability and energy efficiency. Here we exploit a novel approach to high-speed phase encoding and demonstrate a compact, scalable and power efficient integrated quantum transmitter. We encode cryptographic keys on-demand in high repetition rate pulse streams using injection-locking with deterministic phase control at the seed laser. We demonstrate record secure-key-rates under multi-protocol operation. Our modulator-free transmitters enable the development of high-bit rate quantum communications devices, which will be essential for the practical integration of quantum key distribution in high connectivity networks

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries