32 research outputs found
Demonstration of Quantum Nonlocality in presence of Measurement Dependence
Quantum nonlocality stands as a resource for Device Independent Quantum
Information Processing (DIQIP), as, for instance, Device Independent Quantum
Key Distribution. We investigate experimentally the assumption of limited
Measurement Dependence, i.e., that the measurement settings used in Bell
inequality tests or DIQIP are partially influenced by the source of entangled
particle and/or by an adversary. Using a recently derived Bell-like inequality
[Phys. Rev. Lett. 113 190402] and a 99% fidelity source of partially entangled
polarization photonic qubits, we obtain a clear violation of the inequality,
excluding a much larger range of measurement dependent local models than would
be possible with an adapted Clauser, Horne, Shimony and Holt (CHSH) inequality.
It is therefore shown that the Measurement Independence assumption can be
widely relaxed while still demonstrating quantum nonlocality
Towards continuous-wave regime teleportation for light matter quantum relay stations
We report a teleportation experiment involving narrowband entangled photons
at 1560 nm and qubit photons at 795 nm emulated by faint laser pulses. A
nonlinear difference frequency generation stage converts the 795 nm photons to
1560 nm in order to enable interference with one photon out of the pairs, i.e.,
at the same wavelength. The spectral bandwidth of all involved photons is of
about 25 MHz, which is close to the emission bandwidth of emissive quantum
memory devices, notably those based on ensembles of cold atoms and rare earth
ions. This opens the route towards the realization of hybrid quantum nodes,
i.e., combining quantum memories and entanglement-based quantum relays
exploiting either a synchronized (pulsed) or asynchronous (continuous- wave)
scenario
Entanglement distribution over 150 km in wavelength division multiplexed channels for quantum cryptography
7 pages, 5 figuresInternational audienceGranting information privacy is of crucial importance in our society, notably in fiber communication networks. Quantum cryptography provides a unique means to establish, at remote locations, identical strings of genuine random bits, with a level of secrecy unattainable using classical resources. However, several constraints, such as non-optimized photon number statistics and resources, detectors' noise, and optical losses, currently limit the performances in terms of both achievable secret key rates and distances. Here, these issues are addressed using an approach that combines both fundamental and off-the-shelves technological resources. High-quality bipartite photonic entanglement is distributed over a 150 km fiber link, exploiting a wavelength demultiplexing strategy implemented at the end-user locations. It is shown how coincidence rates scale linearly with the number of employed telecommunication channels, with values outperforming previous realizations by almost one order of magnitude. Thanks to its potential of scalability and compliance with device-independent strategies, this system is ready for real quantum applications, notably entanglement-based quantum cryptography
Quantum optical frequency up-conversion for polarisation entangled qubits: towards interconnected quantum information devices
Realising a global quantum network requires combining individual strengths of
different quantum systems to perform universal tasks, notably using flying and
stationary qubits. However, transferring coherently quantum information between
different systems is challenging as they usually feature different properties,
notably in terms of operation wavelength and wavepacket. To circumvent this
problem for quantum photonics systems, we demonstrate a polarisation-preserving
quantum frequency conversion device in which telecom wavelength photons are
converted to the near infrared, at which a variety of quantum memories operate.
Our device is essentially free of noise which we demonstrate through near
perfect single photon state transfer tomography and observation of
high-fidelity entanglement after conversion. In addition, our guided-wave setup
is robust, compact, and easily adaptable to other wavelengths. This approach
therefore represents a major building block towards advantageously connecting
quantum information systems based on light and matter.Comment: 8 pages, 4 figure
Towards a Fully Connected Many-User Entanglement Distribution Quantum Network Within Deployed Telecommunications Fibre-Optic Infrastructure
We present developments in entanglement distribution quantum networks towards a fully connected, scalable, many-user network, which is not limited to simple quantum key distribution protocol