Chip-based quantum key distribution Sibson, P; Erven, C; Godfrey, M ...
Nature communications,
02/2017, Letnik:
8, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Improvement in secure transmission of information is an urgent need for governments, corporations and individuals. Quantum key distribution (QKD) promises security based on the laws of physics and ...has rapidly grown from proof-of-concept to robust demonstrations and deployment of commercial systems. Despite these advances, QKD has not been widely adopted, and large-scale deployment will likely require chip-based devices for improved performance, miniaturization and enhanced functionality. Here we report low error rate, GHz clocked QKD operation of an indium phosphide transmitter chip and a silicon oxynitride receiver chip-monolithically integrated devices using components and manufacturing processes from the telecommunications industry. We use the reconfigurability of these devices to demonstrate three prominent QKD protocols-BB84, Coherent One Way and Differential Phase Shift-with performance comparable to state-of-the-art. These devices, when combined with integrated single photon detectors, pave the way for successfully integrating QKD into future telecommunications networks.
We have investigated the microwave response of a transmon qubit coupled directly to a transmission line. In a transmon qubit, owing to its weak anharmonicity, a single driving field may generate ...dressed states involving more than two bare states. We confirmed the formation of three-state dressed states by observing all of the six associated Rabi sidebands, which appear as either amplification or attenuation of the probe field. The experimental results are reproduced with good precision by a theoretical model incorporating the radiative coupling between the qubit and the microwave.
Entanglement is a fundamental property of quantum mechanics, and is a primary resource in quantum information systems. Its manipulation remains a central challenge in the development of quantum ...technology. In this work, we demonstrate a device which can generate, manipulate, and analyse two-qubit entangled states, using miniature and mass-manufacturable silicon photonics. By combining four photon-pair sources with a reconfigurable six-mode interferometer, embedding a switchable entangling gate, we generate two-qubit entangled states, manipulate their entanglement, and analyse them, all in the same silicon chip. Using quantum state tomography, we show how our source can produce a range of entangled and separable states, and how our switchable controlled-Z gate operates on them, entangling them or making them separable depending on its configuration.
Microporous, non-woven poly(
ε-caprolactone) (PCL) scaffolds were made by electrostatic fiber spinning. In this process, polymer fibers with diameters down to the nanometer range, or nanofibers, are ...formed by subjecting a fluid jet to a high electric field. Mesenchymal stem cells (MSCs) derived from the bone marrow of neonatal rats were cultured, expanded and seeded on electrospun PCL scaffolds. The cell-polymer constructs were cultured with osteogenic supplements under dynamic culture conditions for up to 4 weeks. The cell-polymer constructs maintained the size and shape of the original scaffolds. Scanning electron microscopy (SEM), histological and immunohistochemical examinations were performed. Penetration of cells and abundant extracellular matrix were observed in the cell-polymer constructs after 1 week. SEM showed that the surfaces of the cell-polymer constructs were covered with cell multilayers at 4 weeks. In addition, mineralization and type I collagen were observed at 4 weeks. This suggests that electrospun PCL is a potential candidate scaffold for bone tissue engineering.
Superconducting single-photon detectors (SSPDs) based on NbN nanowires possess properties such as high counting rate, low dark count rate and small timing jitter, which are promising characteristics ...for a quantum key distribution system. An SSPD array has recently attracted attention, because it can provide a higher counting rate, and spatial and photon-number resolutions. We propose readout electronics using single-flux-quantum (SFQ) circuits to process a large number of output signals from an SSPD array. We designed and tested an interface circuit between an SSPD and SFQ circuit, and successfully observed SFQ pulse generation for an input pulse with a current amplitude of 17.4 ~ 36.4 muA , which is comparable with an output current amplitude of the SSPD. The interface circuit was also operational for an input pulse duration of 1.6 ns, which is shorter than the typical recovery time of the SSPD.
We developed a technique for fabricating (100)-oriented NbN thin films on Si (100) wafers by dc magnetron sputtering using TiN as a buffer layer. The lattice constant of the TiN buffer layer measured ...using X-ray diffraction was 0.4242 nm, which is relatively close to the NbN lattice constant of 0.446 nm. Therefore, NbN on the TiN buffer layer was epitaxially grown along the (100) direction. The junctions consisted of epitaxial NbN/AlN/NbN tunnel junctions using a TiN buffer layer fabricated on single-crystal Si (100) substrates. The NbN/AlN/NbN trilayer with the TiN buffer layer exhibited a single-crystal structure with a (200) orientation without other orientations. The gap voltage and the ratio of R sg /R N were approximately 4.9 mV and 100, respectively, for a junctions size of 1.4 × 1.4 μm 2 and J C = 8 A/cm 2 . Here, R sg is the gap resistance at 4 mV, and R N is the junction resistance at 10 mV. These results suggest that the NbN films using the TiN buffer technique offers significant promise for applications in several superconducting devices.
We analysed, fabricated, and characterised niobium nitride (NbN)-based microwave kinetic inductance detectors (MKIDs) with a rewound strip structure (spiral-MKIDs). To control resonance ...characteristics precisely, the linewidth (w) dependence of rewound spiral resonators varying between w = 10, 20, and 40 μm was analysed using an electromagnetic field simulator; the resonance frequencies (f0's) were obtained as 4.42, 4.58, and 5.15 GHz respectively, proving that the inductance decreases as the w increases. To verify the simulation results experimentally, NbN-based MKID arrays with different linewidths were fabricated on 10×10 mm2 sapphire substrates, and cooled down to 3 K. The microwave characteristics with a vector network analyser, and f0's were found to be 4.11, 4.23, and 4.85 GHz for the MKIDs with w = 10, 20, and 40 μm, respectively. These values are in agreement with the simulation results within 7.6% accuracy. The other resonance characteristics such as the scattering-matrix element (S21) and loaded quality factor (QL) showed the similar w dependence with the simulation. Spiral-MKIDs with narrower w is expected to have better detector performance owing to shallower S21 and higher QL.
PDF
