Showing papers by "Cheng-Zhi Peng published in 2010"
TL;DR: In this article, it was shown that up to ten-qubit states can be encoded in five photons, using both their polarization and momentum degrees of freedom, using only five photons.
Abstract: Creating entangled photon states becomes technologically ever more difficult as the number of particles increases, and the current record stands at six entangled photons. However, using both their polarization and momentum degrees of freedom, up to ten-qubit states can be encoded in ‘only’ five photons, as has now been demonstrated.
320 citations
TL;DR: In this article, free-space quantum teleportation through 16 kilometres of air is demonstrated, and the results may pave the way for space-based experiments and global scale quantum communication applications.
Abstract: Researchers demonstrate free-space quantum teleportation through 16 kilometres of air. The results may pave the way for space-based experiments and global scale quantum communication applications.
288 citations
TL;DR: A novel and economic way of synchronization method is designed and incorporated into the system, which allows to work at a low frequency of 40kHz and removes the use of highly precise clock.
Abstract: We report an implementation of decoy-state quantum key distribution (QKD) over 200 km optical fiber cable through photon polarization encoding. This is achieved by constructing the whole QKD system operating at 320 MHz repetition rate, and developing high-speed transmitter and receiver modules. A novel and economic way of synchronization method is designed and incorporated into the system, which allows to work at a low frequency of 40kHz and removes the use of highly precise clock. A final key rate of 15 Hz is distributed within the experimental time of 3089 seconds, by using super-conducting single photon detectors. This is longest decoy-state QKD yet demonstrated up to date. It helps to make a significant step towards practical secure communication in long-distance scope.
226 citations
TL;DR: Real-time voice telephone with one-time pad encoding between any two of the five nodes (four all-pass nodes plus one additional node through relay) is successfully established in the network within 60 km.
Abstract: We have demonstrated a metropolitan all-pass quantum communication network in field fiber for four nodes. Any two nodes of them can be connected in the network to perform quantum key distribution (QKD). An optical switching module is presented that enables arbitrary 2-connectivity among output ports. Integrated QKD terminals are worked out, which can operate either as a transmitter, a receiver, or even both at the same time. Furthermore, an additional link in another city of 60 km fiber (up to 130 km) is seamless integrated into this network based on a trusted relay architecture. On all the links, we have implemented protocol of decoy state scheme. All of necessary electrical hardware, synchronization, feedback control, network software, execution of QKD protocols are made by tailored designing, which allow a completely automatical and stable running. Our system has been put into operation in Hefei in August 2009, and publicly demonstrated during an evaluation conference on quantum network organized by the Chinese Academy of Sciences on August 29, 2009. Real-time voice telephone with one-time pad encoding between any two of the five nodes (four all-pass nodes plus one additional node through relay) is successfully established in the network within 60 km.
198 citations
TL;DR: In this paper, the progress of quantum communication that utilizes photonic entanglement is reviewed and a survey of various methods for generating entangled photons, followed by an introduction of the theoretical principles and the experimental implementations of quantum key distribution.
94 citations
TL;DR: This experiment demonstrates an optical controlled-NOT (CNOT) gate with arbitrary single inputs based on a 4-photon 6-qubit cluster state entangled both in polarization and spatial modes and estimates its quantum process fidelity and proves its entangling capability.
Abstract: We experimentally demonstrate an optical controlled-NOT (CNOT) gate with arbitrary single inputs based on a 4-photon 6-qubit cluster state entangled both in polarization and spatial modes. We first generate the 6-qubit state, and then, by performing single-qubit measurements, the CNOT gate is applied to arbitrary single input qubits. To characterize the performance of the gate, we estimate its quantum process fidelity and prove its entangling capability. In addition, our results show that the gate cannot be reproduced by local operations and classical communication. Our experiment shows that such hyper-entangled cluster states are promising candidates for efficient optical quantum computation.
68 citations
TL;DR: The smallest nontrivial module in such a scheme—a teleportation-based quantum entangling gate for two different photonic qubits is demonstrated—an important step toward the realization of practical quantum computers and could lead to many further applications in linear optics quantum information processing.
Abstract: In recent years, there has been heightened interest in quantum teleportation, which allows for the transfer of unknown quantum states over arbitrary distances. Quantum teleportation not only serves as an essential ingredient in long-distance quantum communication, but also provides enabling technologies for practical quantum computation. Of particular interest is the scheme proposed by D. Gottesman and I. L. Chuang [(1999) Nature 402:390–393], showing that quantum gates can be implemented by teleporting qubits with the help of some special entangled states. Therefore, the construction of a quantum computer can be simply based on some multiparticle entangled states, Bell-state measurements, and single-qubit operations. The feasibility of this scheme relaxes experimental constraints on realizing universal quantum computation. Using two different methods, we demonstrate the smallest nontrivial module in such a scheme—a teleportation-based quantum entangling gate for two different photonic qubits. One uses a high-fidelity six-photon interferometer to realize controlled-NOT gates, and the other uses four-photon hyperentanglement to realize controlled-Phase gates. The results clearly demonstrate the working principles and the entangling capability of the gates. Our experiment represents an important step toward the realization of practical quantum computers and could lead to many further applications in linear optics quantum information processing.
55 citations
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TL;DR: In this paper, an arbitrary unknown quantum state is converted into time bins deterministically in terms of its own polarization using a modified Franson interferometer, which can be used to reject errors and recover the initial state.
Abstract: Error-free transmission (EFT) of quantum information is a crucial ingredient in quantum communication network. To overcome the unavoidable decoherence in noisy channel, to date, many efforts have focused on faithfully transmitting one state by consuming large numbers of synchronized ancillary states. However, huge demands of quantum resources are hard to meet with current technology, thus restrict practical applications. Here we propose and demonstrate an economical method of reliably transmitting quantum information. An arbitrary unknown quantum state is converted into time bins deterministically in terms of its own polarization using a modified Franson interferometer. Any arisen noise in channel will induce an associated error to the reference frame of the time bins, which can be utilized to reject errors and recover the initial state. By virtue of state-independent feature, our method can be applied to entanglement distribution. After passing through 0.8 km randomly twisted optical fiber, the entanglement still survives and is verified. Our approach significantly simplifies the implementation of quantum EFT and enables a general quantum state even entanglement to be protected by feedback, thus can be used as a basic building block in practical long-distance quantum communication network.
2 citations
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TL;DR: In this article, spontaneous parametric down conversion and a 50:50 beam splitter were used to generate coaxial polarization-entangled photon pairs, of which the two photons were far separated from each other.
Abstract: Using spontaneous parametric down conversion and a 50:50 beam splitter, we generate coaxial polarization-entangled photon pairs, of which the two photons are far separated from each other. The photons are then sent one by one through one port of a modified Mach-Zehnder interferometer. We observe interference fringes with a periodicity half of the single-photon wavelength, independent of the distance between the photons. This feature can find applications in quantum-enhanced measurement.