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اطلاعات تماس: مرکز تحقیقات نانوپترونیکس ، دانشکده برق، دانشگاه علم و صنعت ایران، نارمک، تهران ۱۳۱۱۴-۱۶۸۴۴

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  Abstrac: In optical quantum communication, quantum state measurement is necessary. This paper proposes a new technique for realization of polarization filter based on planar lightwave circuit (PLC). This filter is used for quantum state discriminator in quantum communication and also as a Bell-state analyzer in quantum repeater. Electro-optics interferometer has been used in design and implementation of polarization filter. We use lithium niobate as a wafer material and Ti:LiNbO۳ for waveguide. Two directional couplers have been used in this device. The length and spacing of these directional couplers have been designed so that each polarization is routed in specific output. The proposed device has one input and two outputs. If polarization of the input photon is vertical, then this photon will appear in output ۱, otherwise if the input photon has horizontal polarization, it appears in output ۲. For vertical polarization input, the power overlaps integral (POI) shows that isolation between two outputs is ۱۴.۹۶ dB. As to horizontal polarization input, the isolation between two outputs is ۱۳.۸ dB. The designed polarization filter has length of ۳۳mm and width of ۶۰ _ m. This device is very suitable for use in integrated optics.

  Abstrac: Quantum entanglement distribution is an essential part of quantum communication and computation protocols. Here, linear optic elements are employed for the distribution of quantum entanglement over a long distance. Polarization beam splitters and wave plates are used to realize an error-free protocol for broadcasting quantum entanglement in optical quantum communication. This protocol can determine the maximum distance of quantum communication without decoherence. Error detection and error correction are performed in the proposed scheme. In other words, if there is a bit flip along the quantum channel, the end stations (Alice and Bob) can detect this state change and obtain the correct state (entangled photon) at another port. Existing general error detection protocols are based on the quantum controlled-NOT (CNOT) or similar quantum logic operations, which are very difficult to implement experimentally. Here we present a feasible scheme for the implementation of entanglement distribution based on a linear optics element that does not need a quantum CNOT gate.

  Abstrac: In this study, an all optical method will be proposed for quantum entanglement implementation . Universal set of quantum gates will be realized by using Coupled mode theory , interferometric electro-optic modulator and Y-junction beam splitter. Normal modes in waveguides are used as quantum bits and coupled mode equation is derived for optical waveguide modes. This all optical technique can be used to perform any quantum computation. The proposed universal gates have potential of being more compact and easily realized compared to other optical implementations. This method is based on planar lightwave circuit technology and it is suitable for integrated optics.

  Abstract: An all optical method has been proposed for quantum Hadamard gate implementation. This quantum gate was realized by using Y-junction beam splitter. Normal modes in waveguides have been used as quantum bit. This all optical gate can be used in quantum computation and communication. The proposed Hadamard gate has potential of being more compact and easily realized compared to other optical implementations. By using planar lightwave circuit in implementation, the width of Yjunction input waveguide, width of each branch, angle of bend and length of bend were obtained ۱ micron, ۰.۷۵ micron, ۴۵º and ۰.۷۵ micron, respectively. By using planar lightwave circuit in implementation, the radius of large air holes and the radius of small holes were obtained ۰.۲ ands ۰.۱ micron, respectively. The index of substrate was ۱.۳۲۵. Implementation based on photonic crystal structures and planar lightwave circuit technology was used in integrated optics.

  Abstract: in this paper, an all optical method will be proposed for quantum NOT and CNOT gates implementation. These quantum gates will be realized by using interferometric electro-optic modulator. Normal modes in waveguides are used as quantum bits. This all optical technique can be used to perform any quantum computation. The proposed gates have potential of being more compact and easily realized compared to other optical implementations. This method is based on planar lightwave circuit technology and it is suitable for integrated optics.

  Abstract : Entanglement purification is essential to distill highly entangled states from less entangled ones. Existing general purification protocols are based on the quantum controlled-NOT (CNOT) or similar quantum logic operations, which are very difficult to implement experimentally. Here we present a feasible scheme for the implementation of entanglement purification based on planar lightwave circuit (PLC) implementation of quantum CNOT gate. This quantum gate is realized by using interferometric electro-optic modulator. By using planar lightwave circuit in implementation, the width of waveguides and the length of CNOT gate were obtained ۱۲ micron and ۲.۸ cm respectively

  Abstrac: in optical quantum communication, quantum state measurement is necessary. This paper proposes a new technique for realization of polarization filter based on planar lightwave circuit (PLC). This filter is used for quantum state discriminator in quantum communication and also as a bell state analyzer in quantum repeater. Electro-optics interferometer has been used in design and implementation of polarization filter. We use lithium niobate as a wafer material and Ti:LiNbO۳ for waveguide. Two directional couplers have been used in this device. The length and spacing of these directional couplers have been designed so that each polarization is routed in specific output. The proposed device has one input and two outputs. If polarization of the input photon is vertical, then this photon will appear in output ۱, otherwise if the input photon has horizontal polarization, it appears in output ۲. For vertical polarization input, the power overlaps integral (POI) shows that isolation between two outputs is ۱۴.۹۶ dB. As to horizontal polarization input, the isolation between two outputs is ۱۳.۸ dB. The designed polarization filter has length of ۳۳ mm and width of ۶۰ micron. This device is very suitable for use in integrated optics.