Here, we report a proof-of-principle demonstration of five-photon entanglement and open-destination teleportation. In the experiment, we use two entangled photon pairs to generate a four-photon entangled state, which is then combined with a single photon state to achieve the experimental goals. The methods developed in our experiment would

Experimental data reveal that the incorporation of carbonyl groups into polymer matrix can significantly enhance singlet oxygen ((1) O2 ) generation and suppress production of other reactive oxygen species. Excitonic processes investigated by phosphorescence spectroscopy reveal enhanced triplet-exciton generation in the modified g-C3 N4 , which facilitate (1) O2 generation through an energy transfer process. Benefiting from this, the modified g-C3 N4 shows excellent conversion and selectivity in organic synthesis.

We present a realistic purification scheme for pure non-maximally entangled states. In the scheme, Alice and Bob at two distant parties first start with two shared but less entangled photon pairs to produce a conditional four-photon GHZ state, then perform a 45 • polarization measurement onto one of the two photons at each party such that the remaining two photons are projected onto a maximally entangled state. 03.65.Bz, 42.50.Ar

We report an experimental realization of entanglement concentration using two polarizationentangled photon pairs produced by pulsed parametric down-conversion. In the meantime, our setup also provides a proof-in-principle demonstration of a quantum repeater. The quality of our procedure is verified by observing a violation of Bell's inequality by more than 5 standard deviations. The high experimental accuracy achieved in the experiment implies that the requirement of tolerable error rate in multi-stage realization of quantum repeaters can be fulfilled, hence providing a practical toolbox for quantum communication over large distances.

Photoexcitation processes of polymeric carbon nitride were systematically investigated by combining photoluminescence spectroscopy and ultrafast transient absorption spectroscopy, where the identified triplet–triplet annihilation is closely related to the quantum efficiency of photoexcitation applications.

We report the first experimental violation of local realism by four-photon Greenberger-Horne-Zeilinger (GHZ) entanglement. In the experiment, the nonstatistical GHZ conflicts between quantum mechanics and local realism are confirmed, within the experimental accuracy, by four specific measurements of polarization correlations between four photons. In addition, our experimental results also demonstrate a strong violation of Mermin-Ardehali-Belinskii-Klyshko inequality by 76 standard deviations. Such a violation can only be attributed to genuine four-photon entanglement.

Universal logic gates for two quantum bits (qubits) form an essential ingredient of quantum information processing. However, the photons, one of the best candidates for qubits, suffer from the lack of strong nonlinear coupling required for quantum logic operations. Here we show how this drawback can be overcome by reporting a proof-of-principle experimental demonstration of a non-destructive controlled-NOT (CNOT) gate for two independent photons using only linear optical elements in conjunction with single-photon sources and conditional dynamics. Moreover, we have exploited the CNOT gate to discriminate all the four Bell-states in a teleportation experiment. The controlled-NOT (CNOT) or similar logic operations between two individual quantum bits (qubits) are essential for various quantum information protocols such as quantum communication [1,2,3] and quantum computation [4]. In recent years, certain quantum logic gates have been experimentally demonstrated, for example, in ion-traps [5,6] and high-finesse microwave cavities [7]. These achievements open many possibilities for future quantum information processing (QIP) with single atoms. Another promising system for QIP is to use single photons. This is due to the photonic robustness against decoherence and the availability of single-qubit operation. However, it has been very difficult to achieve the necessary logic operations for two individual photonqubits since the physical interaction between photons is much too small. Surprisingly, Knill, Laflamme and Milburn (KLM) has shown that nondeterministic quantum logic operations can be performed using linear optical elements, additional photons (ancilla) and postselection based on the output of single-photon detectors [8]. The original proposal by KLM, though elegant, is not economical in its use of optical components. Various schemes have been proposed to reduce the complexity of the KLM scheme while improve its theoretical efficiency [9, 10, 11]. Remarkably, a recent scheme proposed by Nielsen [12] suggests that without using the elaborate teleportation and Z-measurement error correction in the KLM scheme, any non-trivial linear optical gate that succeeds with finite probability is sufficient to obtain efficient quantum computation. Hence, this scheme significantly simplifies the experimental implementation of linear optical quantum computation (LOQC) A crucial requirement in the schemes of LOQC is the so-called classical feedforwardability, that is, it must be in principle possible to detect when the gate has succeeded by performing some appropriate measurement on ancilla photons [8,12]. This information can then be feedfor- . Conditioned on detecting a |− photon in mode 3 ′ and a |H photon in mode 4 ′ one can implement the CNOT operation between the photons 2 and 5. (b) Quantum circuit for quantum teleportation based on a CNOT gate [17]. By using the CNOT operation, Alice can discriminate the four orthogonal Bell state simultaneously such that a complete teleportation can be achieved.ward for conditional futu...

We develop and exploit a source of two-photon, four-dimensional entanglement to report the first two-particle all-versus-nothing test of local realism with a linear optics setup, but without resorting to a noncontextuality assumption. Our experimental results are in good agreement with quantum mechanics while in extreme contradiction to local realism. Potential applications of our experiment are briefly discussed.