Yury Kurochkin

Deployable networks and regulatory feedback are creating new challenges for quantum communication research. One of the most important challenges highlighted in QKD position papers is the trusted-node concept. At city scale, this problem is already practical issue: 5–50 users may need to share secret keys in an any-to-any topology. In a conventional trusted-node architecture, the telecom operator responsible for the quantum network becomes a trusted organization for all users and all sensitive data. Three approaches can be considered to overcome this limitation: (i) equip every user with both a transmitter and a receiver and use an N × N optical switch [3]; (ii) distribute entanglement between selected user pairs; (iii) use MDI-QKD or TF-QKD with a 2 × N optical switch. In this work, we demonstrate a field deployment of time-shared entanglement distribution between users selected on demand. We consider this approach highly practical because it keeps network management simple and allows the same receiver implementation to be used for every user. Our deployment is located in the Abu Dhabi Global Market (ADGM) free zone in Abu Dhabi. It opens an opportunity for finance-sector clients to test end-user solutions on a quantum-safe network, both by using AES encryptors fed by quantum-generated keys and by applying ETSI GS QKD 014 to request keys at the application layer.

Quantum networks are moving rapidly from research laboratories to practical applications. Most quantum networks are based on the trusted node approach because the distance for quantum key distribution (QKD) is limited by photon loss. Shorter distances quantum networks providing any to any connectivity require N(N-1)/2 dark fiber lines, where N is the number of users. Telecom operators, which are the most active players in quantum networks today, can become trusted node owners, which may be an additional barrier to the adoption of quantum networks. An alternative solution is to use entanglement in quantum networks at the city level. In our work we have demonstrated it on a network with three nodes. The center of the network is the PPLN-based source for polarization entangled photon pairs at 1310 and 1316nm. The outputs of the source are connected to a 2x32 optical switch to which any two users can be connected in pairs. To make the receiver suitable for measuring both photons, we have assembled a 2-wavelength Bragg filter that enables the measurement of photons in both wavelengths with a bandwidth of 2 nm. The receivers are designed to be completely passive - the fiber is connected to the BBM92 polarization projection system in free space box, followed by single photon detectors and a time tagger. Polarization distortion is compensated with a fiber-based polarization controller on the source side using the publicly announced QBER. The key is followed by the standard procedures of sifting, cascade error correction and finite key e=10-10 privacy amplification. The derived keys are uploaded to 10G L2/L3 encryption systems, which are able to establish quantum-safe VPN tunnels between any participants. List below describes results of a key rate for 3 node network when the entangled source is connected to a 2x32 optical switch and its outputs are connected to receivers A1(direct) and A2, A3 with 10 km fiber spools each. All secret key tares include finite key size effects A2 (10 km) - A1 (direct). QBER ~2.8%, Secret key rate ~125 b/s A3 (10 km) - A2 (10km). QBER ~4.9%, Secret key rate ~50 b/s A3 (10 km) - A1 (direct). QBER ~3.9%, Secret key rate ~100 b/s

Randomness is a critical resource of modern cryptosystems. Quantum mechanics offers the best properties of an entropy source for unpredictability. However, these sources are often fragile and can fail silently. Therefore, statistical tests on their outputs should be performed continuously. Testing a sequence for randomness can be very resource-intensive, especially for longer sequences, and transferring this to other systems can put the secrecy at risk. In this paper, we present a method that allows a third party to publicly perform statistical testing without compromising the confidentiality of the random bits by connecting the quality of a public sequence to the private sequence generated using a quantum process. We implemented our protocol over two different optical systems and compared them.

One of the most important requirements for the correct operation of the BB84 protocol is the preparation of the true random state. Most realizations follow this logic: Alice prepares random quantum states, measures them to extract random numbers, and then uses them to modulate the state of the transmitted light. The alternative approach is passive state preparation. It was proposed in 2010 and recently studied for security aspects. The idea is to use the natural phase randomness of the laser pulses to prepare random states. This approach can help to solve the security problem of correlating the state modulation voltage. Originally, the focus was on preparing the polarization state. This required two lasers or an additional intensity modulator. In this work, we use a laser that generates random phase pairs of subsequent pulses as a ready-to-use qubit. This allows us to simplify the Alice device. To perform a full phase characterization, we split a portion of the signal, convert it to polarization, and perform polarization tomography where we postselect four BB84 states. Without a decoy state, this QKD system is well suited for the last mile of a star quantum network with a loss budget of up to 10 dB. We have experimentally demonstrated passive state QKD over 10km deployed and spool fiber obtaining 10-100 bps of secret key correspondingly.

Random number generators are critical components for modern cryptosystems. Deterministic methods of producing random numbers cannot guarantee true randomness due to their susceptibility to external perturbations and deterministic origins. Quantum mechanics due to its probabilistic nature can be used to generate random numbers that cannot be predicted. Here we describe the design of a compact, inexpensive, and manufacturable QRNG based on balanced detection of shot noise from an LED in a commercially available off-the-shelf package which can be integrated into existing devices.

QKD is an emerging industry. Numbers of forecasts indicate rapid growth making it more and more affordable not only to large companies also with the use of service models. At the same time information security is very conservative industry. Digital information security specialists usually do not study quantum mechanics and it cause sense of magic dealing with QKD. The only way to close this gap is education. Most available education solutions focus its efforts on theoretical explanation. Meanwhile if we look at education of telecommunication industry specialists there are a lot of workshops dealing with signal processing equipment. In this work we want to share our experience of creating new competence on World Skills specialists competition. We believe that explanation of QKD via workshops where students can touch by hands optics, electronics and software can change specialist perception from magic to telecommunication equipment.

A remarkable aspect of quantum theory is that certain measurement outcomes are entirely unpredictable to all possible observers. Such quantum events can be harnessed to generate numbers whose randomness is asserted based upon the underlying physical processes. We formally introduce, design, and experimentally demonstrate an ultrafast optical quantum random number generator that uses a totally untrusted photonic source. While considering completely general quantum attacks and using dedicated FPGA hardware for post-processing, we certify and generate in real time random numbers at a rate of 8.05 Gb/s with a composable security parameter of 10^{−10}. Composable security is the most stringent and useful security paradigm because any given protocol remains secure even if arbitrarily combined with other instances of the same, or other, protocols, thereby allowing the generated randomness to be utilized for arbitrary applications in cryptography and beyond. This work achieves the fastest generation of composably secure quantum random numbers ever reported.