19 research outputs found
Asymmetric Quantum Dialogue in Noisy Environment
A notion of asymmetric quantum dialogue (AQD) is introduced. Conventional
protocols of quantum dialogue are essentially symmetric as both the users
(Alice and Bob) can encode the same amount of classical information. In
contrast, the scheme for AQD introduced here provides different amount of
communication powers to Alice and Bob. The proposed scheme, offers an
architecture, where the entangled state and the encoding scheme to be shared
between Alice and Bob depends on the amount of classical information they want
to exchange with each other. The general structure for the AQD scheme has been
obtained using a group theoretic structure of the operators introduced in
(Shukla et al., Phys. Lett. A, 377 (2013) 518). The effect of different types
of noises (e.g., amplitude damping and phase damping noise) on the proposed
scheme is investigated, and it is shown that the proposed AQD is robust and
uses optimized amount of quantum resources.Comment: 11 pages, 2 figure
Quantum e-commerce: A comparative study of possible protocols for online shopping and other tasks related to e-commerce
A set of quantum protocols for online shopping is proposed and analyzed to
establish that it is possible to perform secure online shopping using different
types of quantum resources. Specifically, a single photon based, a Bell state
based and two 3-qubit entangled state based quantum online shopping schemes are
proposed. The Bell state based scheme, being a completely orthogonal state
based protocol, is fundamentally different from the earlier proposed schemes
which were based on conjugate coding. One of the 3-qubit entangled state based
scheme is build on the principle of entanglement swapping which enables us to
accomplish the task without transmission of the message encoded qubits through
the channel. Possible ways of generalizing the entangled state based schemes
proposed here to the schemes which use multiqubit entangled states is also
discussed. Further, all the proposed protocols are shown to be free from the
limitations of the recently proposed protocol of Huang et al. (Quantum Inf.
Process. 14, 2211-2225, 2015) which allows the buyer (Alice) to change her
order at a later time (after initially placing the order and getting it
authenticated by the controller). The proposed schemes are also compared with
the existing schemes using qubit efficiency.Comment: It's shown that quantum e-commerce is not a difficult task, and it
can be done in various way
Quantum cryptography: key distribution and beyond
Uniquely among the sciences, quantum cryptography has driven both
foundational research as well as practical real-life applications. We review
the progress of quantum cryptography in the last decade, covering quantum key
distribution and other applications.Comment: It's a review on quantum cryptography and it is not restricted to QK
Quantum Information Processing with Single Photons
Photons are natural carriers of quantum information due to their ease of
distribution and long lifetime. This thesis concerns various related aspects of
quantum information processing with single photons. Firstly, we demonstrate
N-photon entanglement generation through a generalised N X N symmetric beam
splitter known as the Bell multiport. A wide variety of 4-photon entangled
states as well as the N-photon W-state can be generated with an unexpected
non-monotonic decreasing probability of success with N. We also show how the
same setup can be used to generate multiatom entanglement. A further study of
multiports also leads us to a multiparticle generalisation of the
Hong-Ou-Mandel dip which holds for all Bell multiports of even number of input
ports. Next, we demonstrate a generalised linear optics based photon filter
that has a constant success probability regardless of the number of photons
involved. This filter has the highest reported success probability and is
interferometrically robust. Finally, we demonstrate how repeat-until-success
quantum computing can be performed with two distant nodes with unit success
probability using only linear optics resource. We further show that using
non-identical photon sources, robustness can still be achieved, an illustration
of the nature and advantages of measurement-based quantum computation. A direct
application to the same setup leads naturally to arbitrary multiphoton state
generation on demand. Finally, we demonstrate how polarisation entanglement of
photons can be detected from the emission of two atoms in a Young's double-slit
type experiment without linear optics, resulting in both atoms being also
maximally entangled.Comment: PhD Thesis, 131 page