arXiv subjects

Anirban Pathak

Publications and source records attributed to Anirban Pathak.

At least 145 records · Page 8Linked to original sources

arXiv2013

Hierarchical quantum communication

A general approach to study the hierarchical quantum information splitting (HQIS) is proposed and the same is used to systematically investigate the possibility of realizing HQIS using different classes of 4-qubit entangled states that are not connected by SLOCC. Explicit examples of HQIS using 4-qubit cluster state and 4-qubit |Ω> state are provided. Further, the proposed HQIS scheme is generalized to introduce two new aspects of hierarchical quantum communication. To be precise, schemes of probabilistic hierarchical quantum information splitting and hierarchical quantum secret sharing are obtained by modifying the proposed HQIS scheme. A number of practical situations where hierarchical quantum communication would be of use are also presented.

quant-ph↗

arXiv2013

Intermodal entanglement in Raman processes

The operator solution of a completely quantum mechanical Hamiltonian of the Raman processes is used here to investigate the possibility of obtaining intermodal entanglement between different modes involved in the Raman processes (e.g. pump mode, Stokes mode, vibration (phonon) mode and anti-Stokes mode). Intermodal entanglement is reported between a) pump mode and anti-Stokes mode, b) pump mode and vibration (phonon) mode c) Stokes mode and vibration phonon mode, d) Stokes mode and anti-stokes mode in the stimulated Raman processes for the variation of the phase angle of complex eigenvalue $α_{1}$ of pump mode $a$. Some incidents of intermodal entanglement in the spontaneous and the partially spontaneous Raman processes are also reported. Further it is shown that the specific choice of coupling constants may produce genuine entanglement among Stokes mode, anti-Stokes mode and vibration-phonon mode. It is also shown that the two mode entanglement not identified by Duan's criterion may be identified by Hillery-Zubairy criteria. It is further shown that intermodal entanglement, intermodal antibunching and intermodal squeezing are independent phenomena.

quant-ph↗

arXiv2012

Relation between squeezing of vacuum fluctuations, quantum entanglement and sub-shot noise in Raman scattering

A completely quantum description of Raman process is used to investigate the nonclassical properties of the modes in the stimulated, spontaneous and partially spontaneous Raman process. Both coherent scattering (where all the initial modes are coherent) and chaotic scattering (where initial phonon mode is chaotic and all the other modes are coherent) are studied. Nonclassical character of Raman process is observed by means of intermodal entanglement, single mode and intermodal squeezing of vacuum fluctuations, sub-shot noise and wave variances. Joint photon-phonon number and integrated-intensity distributions are then used to illustrate the observed nonclassicalities. Conditional and difference number distributions are also provided to illustrate the nonclassical character. The mutual relation between the obtained nonclassicalities and their variations dependent on phases, rescalled time and ratio of coupling constants are also reported.

quant-ph↗

arXiv2012

Beyond the Goldenberg-Vaidman protocol: Secure and efficient quantum communication using arbitrary, orthogonal, multi-particle quantum states

It is shown that maximally efficient protocols for secure direct quantum communications can be constructed using any arbitrary orthogonal basis. This establishes that no set of quantum states (e.g. GHZ states, W states, Brown states or Cluster states) has an advantage over the others, barring the relative difficulty in physical implementation. The work provides a wide choice of states for experimental realization of direct secure quantum communication protocols. We have also shown that this protocol can be generalized to a completely orthogonal state based protocol of Goldenberg-Vaidman (GV) type. The security of these protocols essentially arises from duality and monogamy of entanglement. This stands in contrast to protocols that employ non-orthogonal states, like Bennett-Brassard 1984 (BB84), where the security essentially comes from non-commutativity in the observable algebra.

quant-ph↗

arXiv2012

Improved protocols of secure quantum communication using W states

Recently, Hwang et al. [Eur. Phys. J. D. 61, 785 (2011)] and Yuan et al. [Int. J. Theo. Phys. 50, 2403 (2011)] have proposed two efficient protocols of secure quantum communication using 3-qubit and 4-qubit symmetric W state respectively. These two dense coding based protocols are generalized and their efficiencies are considerably improved. Simple bounds on the qubit efficiency of deterministic secure quantum communication (DSQC) and quantum secure direct communication (QSDC) protocols are obtained and it is shown that dense coding is not essential for designing of maximally efficient DSQC and QSDC protocols. This fact is used to design maximally efficient protocols of DSQC and QSDC using 3-qubit and 4-qubit W states.

quant-ph↗

arXiv2012

On the group theoretic structure of a class of quantum dialogue protocols

Intrinsic symmetry of the existing protocols of quantum dialogue are explored. It is shown that if we have a set of mutually orthogonal $n$-qubit states {\normalsize $\{|ϕ_{0}>,|ϕ_{1}>,....,|ϕ_{i}<,...,|ϕ_{2^{n}-1}>\}$ and a set of $m-qubit$ ($m\leq n$) unitary operators $\{U_{0},U_{2},...,U_{2^{n}-1}\}:U_{i}|ϕ_{0}>=|ϕ_{i}>$ and $\{U_{0},U_{2},...,U_{2^{n}-1}\}$ forms a group under multiplication then it would be sufficient to construct a quantum dialogue protocol using this set of quantum states and this group of unitary operators}. The sufficiency condition is used to provide a generalized protocol of quantum dialogue. Further the basic concepts of group theory and quantum mechanics are used here to systematically generate several examples of possible groups of unitary operators that may be used for implementation of quantum dialogue. A large number of examples of quantum states that may be used to implement the generalized quantum dialogue protocol using these groups of unitary operators are also obtained. For example, it is shown that GHZ state, GHZ-like state, W state, 4 and 5 qubit Cluster states, Omega state, Brown state, $Q_{4}$ state and $Q_{5}$ state can be used for implementation of quantum dialogue protocol. The security and efficiency of the proposed protocol is appropriately analyzed. It is also shown that if a group of unitary operators and a set of mutually orthogonal states are found to be suitable for quantum dialogue then they can be used to provide solutions of socialist millionaire problem.

quant-ph↗

arXiv2012

Efficient protocols for deterministic secure quantum communication using GHZ-like states

Two protocols for deterministic secure quantum communication (DSQC) using GHZ-like states have been proposed. It is shown that one of these protocols can be modified to an equivalent but more efficient protocol of quantum secure direct communication (QSDC). Security and efficiency of the proposed protocols are analyzed in detail and are critically compared with the existing protocols. It is shown that the proposed protocols are highly efficient. It is also shown that all the physical systems where dense coding is possible can be used to design maximally efficient protocol of DSQC and QSDC. Further, it is shown that dense coding is sufficient but not essential for DSQC and QSDC protocols of the present kind. We have shown that there exist a large class of quantum state which can be used to design maximally efficient DSQC and QSDC protocols of the present kind. It is further, observed that maximally efficient QSDC protocols are more efficient than their DSQC counterparts. This additional efficiency arises at the cost of message transmission rate.

quant-ph↗

arXiv2011

The quantum cryptographic switch

We illustrate using a quantum system the principle of a cryptographic switch, in which a third party (Charlie) can control to a continuously varying degree the amount of information the receiver (Bob) receives, after the sender (Alice) has sent her information. Suppose Charlie transmits a Bell state to Alice and Bob. Alice uses dense coding to transmit two bits to Bob. Only if the 2-bit information corresponding to choice of Bell state is made available by Charlie to Bob can the latter recover Alice's information. By varying the information he gives, Charlie can continuously vary the information recovered by Bob. The performance of the protocol subjected to the squeezed generalized amplitude damping channel is considered. We also present a number of practical situations where a cryptographic switch would be of use.

quant-ph↗

arXiv2010

Study of Proton Transfer Reaction Dynamics in Pyrrole 2-Carboxyldehyde

Photophysical and photochemical dynamics of ground state and excited state proton transfer reaction is reported for Pyrrole 2-Carboxyldehyde (PCL). Steady state absorption and emission measurements are conducted in PCL. The theoretical investigation is done by using different quantum mechanical methods (e.g. Hartree Fock, DFT, MP2, CCSD etc.). The reaction pathway and two dimensional potential energy surfaces are computed in various level of theory. A transition state is also reported in gas phase and reaction filed calculation. It is established that PCL forms different emitting species in different media. A large Stokes shifted emission band, which is attributed to species undergoing excited state intramolecular proton transfer, is observed in hydrocarbon solvent. Intermolecular proton transfer is observed in hydroxylic polar solvent. Experimental observations yield all possible signatures of intramolecular and intermolecular proton transfer in excited state of PCL. The origins of these signatures have been explained successfully using corresponding quantum mechanical theories.

physics.atm-clus↗

arXiv2010

Comment on Quantum teleportation via GHZ-like state

Recently Yang et al. [Int. J. Theo. Phys. 48 (2009) 516] have shown that an unknown qubit can be teleported by using a particular GHZ-like state as quantum channel. However, there are several errors in the calculation which lead to incorrect conclusions. The errors have been indicated and corrected. It is also noted that their scheme and the independently proposed teleportation scheme of Zhang et al. [Int. J. Theo. Phys. 48 (2009) 3331] uses quantum channel from the same family and any state of that family may be used for teleportation.

quant-ph↗

arXiv2010

Efficient quantum circuits for perfect and controlled teleportation of n-qubit non-maximally entangled states of generalized Bell-type

An efficient and economical scheme is proposed for the perfect quantum teleportation of n-qubit non-maximally entangled state of generalized Bell-type. A Bell state is used as the quantum channel in the proposed scheme. It is also shown that the controlled teleportation of this n-qubit state can be achieved by using a GHZ state or a GHZ-like state as quantum channel. The proposed schemes are economical because for the perfect and controlled teleportation of n-qubit non-maximally entangled state of generalized Bell-type we only need a Bell state and a tripartite entangled state respectively. It is also established that there exists a family of 12 orthogonal tripartite GHZ-like states which can be used as quantum channel for controlled teleportation. The proposed protocols are critically compared with the existing protocols.

quant-ph↗

arXiv2010

Higher Order Squeezing and Higher Order Subpoissonian Photon Statistics in Intermediate States

Recently simpler criteria for the Hong-Mandel higher order squeezing (HOS) and higher order subpossonian photon statistics (HOSPS) are provided by us [Phys. Lett. A 374 (2010) 1009]. Here we have used these simplified criteria to study the possibilities of observing HOSPS and HOS in different intermediate states, such as generalized binomial state, hypergeometric state, negative binomial state and photon added coherent state. It is shown that these states may satisfy the condition of HOS and HOSPS. It is also shown that the depth and region of nonclassicality can be controlled by controlling various parameters related to intermediate states. Further, we have analyzed the mutual relationship between different signatures of higher order nonclassicality with reference to these intermediate states. We have observed that the generalized binomial state may show signature of HOSPS in absence of HOS. Earlier we have shown that NLVSS shows HOS in absence of HOSPS. Consequently it is established that the HOSPS and HOS of same order are independent phenomenon.

quant-ph↗

arXiv2010

An algorithm for minimization of quantum cost

A new algorithm for minimization of quantum cost of quantum circuits has been designed. The quantum cost of different quantum circuits of particular interest (eg. circuits for EPR, quantum teleportation, shor code and different quantum arithmetic operations) are computed by using the proposed algorithm. The quantum costs obtained using the proposed algorithm is compared with the existing results and it is found that the algorithm has produced minimum quantum cost in all cases.

quant-ph↗

arXiv2009

Higher order antibunching and subpossonian photon statistics in five wave mixing process

We have investigated the possibility of observing higher order antibunching (HOA) and higher order subpossonian photon statistics (HOSPS) in five wave mixing and third harmonic generation process. It had been shown that both processes satisfy the criteria of HOA and HOSPS. Further, some observations on the nature of interaction which produces HOA and HOSPS are reported.

quant-ph↗

arXiv2009

Which optical processes are suitable to make probabilistic single photon sources for quantum cryptography?

Single photon sources to be used in quantum cryptography must show higher order antibunching (HOA). HOA is reported by us in several many wave mixing processes. In the present work we have investigated the possibility of observing HOA in multiwave mixing processes in general. The generalized Hamiltonian is solved for several particular cases in Heisenberg picture and possibility of observing HOA is investigated with the help of criterion of Pathak and Garcia. Several particular cases of the generalized Hamiltonian are solved with the help of short time approximation technique and HOA is reported for pump modes of different multiwave mixing processes. It is also found that HOA can not be observed for the signal and stokes modes in of the cases studied here.

quant-ph↗

arXiv2009

New designs of reversible sequential devices

A clear protocol for synthesis of sequential reversible circuits from any particular gate library has been provided. Using that protocol, reversible circuits for SR latch, D latch, JK latch and T latch are designed from NCT gate library. All the circuits have been optimized with the help of existing local optimization algorithms (e.g. template matching, moving rule and deletion rule). It has been shown that the present proposals have lower gate complexities, lower number of garbage bits, lower quantum cost and lower number of feedback loops compared to the earlier proposals. For a fair comparison, the optimized sequential circuits have been compared with the earlier proposals for the same after converting the earlier proposed circuits into equivalent NCT circuits. Further, we have shown that the advantage in gate count obtained in some of the earlier proposals by introduction of New gates is an artifact and if it is allowed then every reversible circuit block can be reduced to a single gate. In this context, some important conceptual issues related to the designing and optimization of sequential reversible circuits have been addressed. A protocol for minimization of quantum cost of reversible circuit has also been proposed here.

quant-ph↗

arXiv2009

An analysis of reversible multiplier circuits

Multiplier circuits play an important role in reversible computation, which is helpful in diverse areas such as low power CMOS design, optical computing, DNA computing and bioinformatics. Here we propose a new reversible multiplier circuit with optimized hardware complexity. The optimized multiplier circuit is compared with the earlier proposals. We have shown that the quantum cost of earlier proposals can be further reduced with the help of existing local optimization algorithms (e.g. template matching, moving rule and deletion rule). A systematic protocol for reduction of quantum cost has been proposed. It has also been shown that the advantage in gate count obtained in some of the earlier proposals by introduction of new reversible gates is an artifact and if it is allowed then every circuit block can be reduced to a single gate. Further, it is shown that the 4x4 reversible gates proposed for designing of a component of multiplier circuit (full adder) is neither unique nor special and many such 4x4 gates may be proposed. As example three such new gates have been presented here and it is shown that the proposed gates are universal. It is also shown that the total cost of our design is minimum.

quant-ph↗

arXiv2009

Probabilistic model of fault detection in quantum circuits

It is shown that the fault testing for quantum circuits does not follow conventional classical techniques. If probabilistic gate like Hadamard gate is included in a circuit then the classical notion of test vector is shown to fail. We have reported several new and distinguishing features of quantum fault and also presented a general methodology for detection of functional faults in a quantum circuit. The technique can generate test vectors for detection of different kinds of fault. Specific examples are given and time complexity of the proposed quantum fault detection algorithm is reported.

quant-ph↗