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:: Quantronics laboratory ::

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Quantronics Lab

1- Introduction
2- People
3- Projects and Research Activities
4- Equipments of Optoelectronics Lab.
5- Recent Conference and Journal Papers5- Recent Conference and Journal Papers
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Introduction

Quantronics is composed of two words: Quantum and Electronics. Thus contains two scientific fields. The main research activity of this laboratory is quantum communication and optical quantum computation.
Quantum entanglement lays at the heart of quantum information processing (QIP) , which over the past twenty years has become an emerging field of modern physics. QIP can mainly be divided into the two areas of quantum communication and quantum computation. Quantum communication describes the transfer of quantum states over large distances, which can lead to drastic improvements in security – quantum cryptography – and channel capacity – quantum dense coding. It further covers the distribution of bi- or multi-partite entanglement between different parties, separated by large distances.
Quantum computation is dedicated to the implementation of algorithms that exploit the superposition character of quantum entanglement to dramatically speed up computational tasks such as a reduction of time needed to search an unsorted database of N elements. Any classical algorithm necessitates N operations to accomplish this task, whereas a quantum algorithm only needs N1/2 operations. Probably the most famous quantum algorithm is Shor’s algorithm to factorize large numbers. Its introduction in 1994 has jump started and fueled tremendous effort in the new field of QIP, both on the theoretical and experimental side.


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People

 Masoomeh Taherkhani 

Contact Information :


Nanoptronics Research Center, Electronics and Electrical Engineering Department, Iran University of Science and Technology, Narmak, Tehran, Iran
Tel.: (+98) 21-73222667
E-mail: m_taherkhani@iust.ac.ir
For more information please click here.


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Projects

 Design and Modeling of Quantum Repeater in Long-distance Quantum Communication

Quantum communication system transmits quantum information from one point to another point. Distribution and control of entanglement in global scale is required in long-distance quantum communication. Now, the only suitable system for long-distance quantum communication is photon. Photon-based protocols suffer from photon loss and quantum decoherence in quantum channels. These problems limit range of single photon transmission up to several tens of kilometers in silica fibers. This problem can be solved by dividing the long distances into shorter intervals, so that the entanglement can be preserved in the shorter distances. System, which is responsible for this task, is called quantum repeater.

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 Linear optics quantum computing

Quantum computing has attracted much attention over the last 2 decades, partly because of its promise of superfast factoring and its potential for the efficient simulation of quantum dynamics. There are many different architectures for quantum computers based on many different physical systems. All of these systems have their own advantages in quantum information processing but no physical implementation seems to have a clear edge over others at this point. Optical quantum systems are prominent candidates for quantum computing, since they provide a natural integration of quantum computation and quantum communication. There are several proposals for building quantum computers that manipulate the state of light, ranging from cat-state logic to encoding a qubit in a harmonic oscillator and optical continuous-variable quantum computing. The main difficulty with any optical approach is that nonlinear interactions between individual photons are required in order to implement quantum logic gates that operate with 100% efficiency.


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Equipments

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 Single Photon Counter

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 Nonlinear Crystal BBO-610H

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 Single photon Detectors

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Conference and Journal

Recent Conference and Journal Papers5- Recent Conference and Journal Papers

1. S. Salemian, S. Mohammadnejad, “ Design and implementation of polarization filter for quantum states discriminator in optical quantum communication ,” Optik 122 (2011) 349–354

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:LiNbO3 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 1, otherwise if the input photon has horizontal polarization, it appears in output 2. For vertical polarization input, the power overlaps integral (POI) shows that isolation between two outputs is 14.96 dB. As to horizontal polarization input, the isolation between two outputs is 13.8 dB. The designed polarization filter has length of 33mm and width of 60 _ m. This device is very suitable for use in integrated optics.

2. S. Salemian, S. Mohammadnejad, “ An error-free protocol for quantum entanglement distribution in long-distance quantum communication ,” Chinese Science Bulletin , Vol. 56, No.7, pp. 618-625, Mar 2011

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.

3. Sh. Salemian and Sh. Mohammadnejad , " Quantum Entanglement Implementation Using Interferometric Electro-Optic Modulator and Coupled Mode Theory ", Journal of Applied Sciences 8 (5): 743-752, 2008

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.

4. Sh. Salemian and Sh. Mohammadnejad, " Quantum Hadamard Gate Implementation Using Planar Lightwave Circuit and Photonic Crystal Structures " , American Journal of Applied Sciences 5(9): 1144-1148, 2008

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 1 micron, 0.75 micron, 45º and 0.75 micron, respectively. By using planar lightwave circuit in implementation, the radius of large air holes and the radius of small holes were obtained 0.2 ands 0.1 micron, respectively. The index of substrate was 1.325. Implementation based on photonic crystal structures and planar lightwave circuit technology was used in integrated optics.

5. Sh. Salemian and Sh. Mohammadnejad, " Quantum NOT and CNOT Gates Implementation Using Interferometric Electro-Optic Modulator ", 16th Iranian Conference on Electrical Engineering, Tarbiat Modares University, 2008

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.

6. Sh. Salemian and Sh. Mohammadnejad, " A Novel Approach to Implementation of Quantum Entanglement Purification in Optical Quantum Communication ", 6th Symposium on Communication Systems, Networks and Digital Signal Processing, Graz University of Technology, 2008

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 12 micron and 2.8 cm respectively

7. Sh. Salemian and Sh. Mohammadnejad, " Design and Implementation of Polarization Filter for Quantum States Discriminator in Optical Quantum Communication ", 17th Iranian Conference on Electrical Engineering, IUST, 2009

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:LiNbO3 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 1, otherwise if the input photon has horizontal polarization, it appears in output 2. For vertical polarization input, the power overlaps integral (POI) shows that isolation between two outputs is 14.96 dB. As to horizontal polarization input, the isolation between two outputs is 13.8 dB. The designed polarization filter has length of 33 mm and width of 60 micron. This device is very suitable for use in integrated optics.

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