249 research outputs found
Quantum networks with chiral light--matter interaction in waveguides
We propose a scalable architecture for a quantum network based on a simple
on-chip photonic circuit that performs loss-tolerant two-qubit measurements.
The circuit consists of two quantum emitters positioned in the arms of an
on-chip Mach-Zehnder interferometer composed of waveguides with chiral
light--matter interfaces. The efficient chiral light--matter interaction allows
the emitters to perform high-fidelity intranode two-qubit parity measurements
within a single chip, and to emit photons to generate internode entanglement,
without any need for reconfiguration. We show that by connecting multiple
circuits of this kind into a quantum network, it is possible to perform
universal quantum computation with heralded two-qubit gate fidelities achievable in state-of-the-art quantum dot systems.Comment: 5 pages plus supplementary materia
Hong-Ou-Mandel interference of polarization qubits stored in independent room-temperature quantum memories
First generation quantum repeater networks require independent quantum
memories capable of storing and retrieving indistinguishable photons to perform
quantum-interference-mediated high-repetition entanglement swapping operations.
The ability to perform these coherent operations at room temperature is of
prime importance in order to realize large scalable quantum networks. Here we
address these significant challenges by observing Hong-Ou-Mandel (HOM)
interference between indistinguishable photons carrying polarization qubits
retrieved from two independent room-temperature quantum memories. Our
elementary quantum network configuration includes: (i) two independent sources
generating polarization-encoded qubits; (ii) two atomic-vapor dual-rail quantum
memories; and (iii) a HOM interference node. We obtained interference
visibilities after quantum memory retrieval of for few-photon level inputs and for single-photon level inputs. Our prototype
network lays the groundwork for future large-scale memory-assisted quantum
cryptography and distributed quantum networks.Comment: 12 pages, 6 figure
Quantum information with Gaussian states
Quantum optical Gaussian states are a type of important robust quantum states
which are manipulatable by the existing technologies. So far, most of the
important quantum information experiments are done with such states, including
bright Gaussian light and weak Gaussian light. Extending the existing results
of quantum information with discrete quantum states to the case of continuous
variable quantum states is an interesting theoretical job. The quantum Gaussian
states play a central role in such a case. We review the properties and
applications of Gaussian states in quantum information with emphasis on the
fundamental concepts, the calculation techniques and the effects of
imperfections of the real-life experimental setups.
Topics here include the elementary properties of Gaussian states and relevant
quantum information device, entanglement-based quantum tasks such as quantum
teleportation, quantum cryptography with weak and strong Gaussian states and
the quantum channel capacity, mathematical theory of quantum entanglement and
state estimation for Gaussian states.Comment: 170 pages. Minors of the published version are corrected and listed
in the Acknowledgement part of this versio
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