Coupled-mode theory of the Raman effect in silicon-on-insulator waveguides

Coupled-mode theory is used to calculate Raman gain and spontaneous efficiency in silicon waveguides with cross-sectional areas ranging from 0.16 to 16 microm2. We find a monotonic increase in the Raman gain as the waveguide cross section decreases for the range of dimensions considered. It is also found that mode coupling between the Stokes modes is insignificant, and thus polarization multiplexing is possible. The results also demonstrate that for submicrometer waveguide dimensions the Einstein relation between spontaneous efficiency and stimulated gain no longer holds.     

The Cost Reduction of Distributed Quantum Factorization Circuits

International Journal of Theoretical Physics - The number of qubits involved in a quantum system increases as the quantum computation is being progressed. Restrictions in monolithic quantum...     

An Evolutionary Approach to Optimizing Teleportation Cost in Distributed Quantum Computation

International Journal of Theoretical Physics - Distributed quantum computing has been well-known for many years as a system composed of a number of small-capacity quantum circuits. Limitations in...     

Bidirectional Quantum Teleportation of a Class of <Emphasis Type="Italic">n</Emphasis>-Qubit States by Using (2<Emphasis Type="Italic">n</Emphasis> + <Emphasis Type="Bold">2</Emphasis>)-Qubit Entangled States as Quantum Channel

A new protocol of bidirectional quantum teleportation (BQT) is proposed in which the users can transmit a class of n-qubit state to each other simultaneously, by using (2n + 2)-qubit entangled states as quantum channel. The state of the art approaches can only transmit two-qubit states in each round. This scheme is based on control-not operation, single-qubit measurements and appropriate single-qubit unitary operations. It is shown that the protocol is secure in preparation phase.     

n-Bit Quantum Secret Sharing Protocol Using Quantum Secure Direct Communication

International Journal of Theoretical Physics - The proposed quantum secret sharing protocol in this article conveys n bit secret messages from the sender to the n receivers making use of a secure...     

A Robust Blind Quantum Copyright Protection Method for Colored Images Based on Owner’s Signature

Watermarking is the imperceptible embedding of watermark bits into multimedia data in order to use for different applications. Among all its applications, copyright protection is the most prominent usage which conceals information about the owner in the carrier, so as to prohibit others from assertion copyright. This application requires high level of robustness. In this paper, a new blind quantum copyright protection method based on owners’s signature in RGB images is proposed. The method utilizes one of the RGB channels as indicator and two remained channels are used for embedding information about the owner. In our contribution the owner’s signature is considered as a text. Therefore, in order to embed in colored image as watermark, a new quantum representation of text based on ASCII character set is offered. Experimental results which are analyzed in MATLAB environment, exhibit that the presented scheme shows good performance against attacks and can be used to find out who the real owner is. Finally, the discussed quantum copyright protection method is compared with a related work that our analysis confirm that the presented scheme is more secure and applicable than the previous ones currently found in the literature.     

Optimizing Teleportation Cost in Distributed Quantum Circuits

International Journal of Theoretical Physics - The presented work provides a procedure for optimizing the communication cost of a distributed quantum circuit (DQC) in terms of the number of qubit...     

An Anonymous Surveying Protocol via Greenberger-Horne-Zeilinger States

A new experimentally feasible anonymous survey protocol with authentication using Greenberger-Horne-Zeilinger (GHZ) entangled states is proposed. In this protocol, a chief executive officer (CEO) of a firm or company is trying to find out the effect of a possible action. In order to prepare a fair voting, the CEO would like to make an anonymous survey and is also interested in the total action for the whole company and he doesn’t want to have a partial estimate for each department. In our proposal, there are two voters, Alice and Bob, voting on a question with a response of either ”yes” or ”no” and a tallyman, whose responsibility is to determine whether they have cast the same vote or not. In the proposed protocol the total response of the voters is calculated without revealing the actual votes of the voters.     

Ultrasonic reflection mode imaging of the nonlinear parameter B/A. II: Signal processing

The nonlinear acoustic interaction between a reflected single-frequency sinusoid and a broadband pump waveform propagating in the opposite direction produces phase changes in the probe proportional to the nonlinear parameter B/A in the spatial region of interaction. The instantaneous phase change along the received probe can be expressed as the convolution of the pump waveform with the spatial distribution of B/A along the propagation path over which the pump and reflected probe interact. In theory, the phase modulated sinusoidal probe can be processed (phase detection and deconvolution) to produce an "A-mode" representation of B/A. If the pump is an intense unipolar impulse and the probe a swept-frequency sinusoid, then the pump interacts with the probe at each point along the propagation path at a unique frequency. Thus the phase modulation that carries information about the spatial distribution of B/A can be extracted from the phase spectrum by a simple Fourier transformation analogous to the space to frequency mapping so basic to magnetic resonance imaging. If the impulsive pump is replaced by another swept-frequency sinusoid, then the phase change in the probe due to B/A at a particular point along the propagation path will be spread out for the duration of the pump along the probe. Passage of the received signal through an appropriate matched filter restores spatial coherence to the phase information in the probe so that it can be processed as if the pump were a broadbanded impulse. This approach suggests a means of approaching the design of effective pump waveforms that can resolve a wide range of spatial frequencies in (B/A)(x).     

Bidirectional Teleportation of a Two-Qubit State by Using Eight-Qubit Entangled State as a Quantum Channel

In this paper, a new scheme of bidirectional quantum teleportation (BQT) making use of an eight-qubit entangled state as the quantum channel is presented. This scheme is the first protocol without controller by which the users can teleport an arbitrary two-qubit state to each other simultaneously. This protocol is based on the ControlledNOT operation, appropriate single-qubit unitary operations and single-qubit measurement in the Z-basis and X-basis.