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1.
Phys Rev Lett ; 123(10): 100503, 2019 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-31573287

RESUMO

Quantum computing has seen tremendous progress in past years. Due to implementation complexity and cost, the future path of quantum computation is strongly believed to delegate computational tasks to powerful quantum servers on the cloud. Universal blind quantum computing (UBQC) provides the protocol for the secure delegation of arbitrary quantum computations, and it has received significant attention. However, a great challenge in UBQC is how to transmit a quantum state over a long distance securely and reliably. Here, we solve this challenge by proposing a resource-efficient remote blind qubit preparation (RBQP) protocol, with weak coherent pulses for the client to produce, using a compact and low-cost laser. We experimentally verify a key step of RBQP-quantum nondemolition measurement-in the field test over 100 km of fiber. Our experiment uses a quantum teleportation setup in the telecom wavelength and generates 1000 secure qubits with an average fidelity of (86.9±1.5)%, which exceeds the quantum no-cloning fidelity of equatorial qubit states. The results prove the feasibility of UBQC over long distances, and thus serves as a key milestone towards secure cloud quantum computing.

2.
Phys Rev Lett ; 122(9): 090404, 2019 Mar 08.
Artigo em Inglês | MEDLINE | ID: mdl-30932520

RESUMO

We derive a state-dependent error-disturbance trade-off based on a statistical distance in the sequential measurements of a pair of noncommutative observables and experimentally verify the relation with a photonic qubit system. We anticipate that this Letter may further stimulate the study on the quantum uncertainty principle and related applications in quantum measurements.

3.
Phys Rev Lett ; 112(1): 010504, 2014 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-24483878

RESUMO

Quantum physics allows for unconditionally secure communication between parties that trust each other. However, when the parties do not trust each other such as in the bit commitment scenario, quantum physics is not enough to guarantee security unless extra assumptions are made. Unconditionally secure bit commitment only becomes feasible when quantum physics is combined with relativistic causality constraints. Here we experimentally implement a quantum bit commitment protocol with relativistic constraints that offers unconditional security. The commitment is made through quantum measurements in two quantum key distribution systems in which the results are transmitted via free-space optical communication to two agents separated with more than 20 km. The security of the protocol relies on the properties of quantum information and relativity theory. In each run of the experiment, a bit is successfully committed with less than 5.68×10(-2) cheating probability. This demonstrates the experimental feasibility of quantum communication with relativistic constraints.

4.
Opt Lett ; 38(23): 4985-7, 2013 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-24281489

RESUMO

We have demonstrated upconversion detection at the single photon level in the 2 µm spectral window using a pump wavelength near 1550 nm, a periodically poled lithium niobate (PPLN) waveguide, and a volume Bragg grating (VBG) to reduce noise. We achieve a system photon detection efficiency of 10%, with a noise count rate of 24,500 counts per second, competitive with other 2 µm single photon detection technologies. This detector has potential applications in environmental gas monitoring, life science, and classical and quantum communication.

5.
Opt Express ; 21(21): 24674-9, 2013 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-24150311

RESUMO

We demonstrate a photon-counting optical time-domain reflectometry with 42.19 dB dynamic range using an ultra-low noise up-conversion single photon detector. By employing the long-wave pump technique and a volume Bragg grating, we achieve a noise equivalent power of -139.7 dBm/√Hz for our detector. We perform the OTDR experiments using a fiber of length approximate 217 km, and show that our system can identify defects along the entire fiber length in a measurement time of 13 minutes.

6.
Opt Express ; 21(12): 13986-91, 2013 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-23787588

RESUMO

We demonstrate up-conversion single-photon detection for the 1550-nm telecommunications band using a PPLN waveguide, long-wavelength pump, and narrowband filtering using a volume Bragg grating. We achieve total-system detection efficiency of around 30% with noise at the dark-count level of a Silicon APD. Based on the new detector, a single-pixel up-conversion infrared spectrometer with a noise equivalent power of -142 dBm Hz(-1/2) was demonstrated, which was as good as a liquid nitrogen cooled CCD camera.


Assuntos
Refratometria/instrumentação , Análise Espectral/instrumentação , Ressonância de Plasmônio de Superfície/instrumentação , Telecomunicações/instrumentação , Transdutores , Desenho de Equipamento , Análise de Falha de Equipamento , Razão Sinal-Ruído
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