9 research outputs found
Implementation of coherent one way protocol for quantum key distribution up to an effective distance of 145 km
In the present work, we report experimental realization of an optical fiber
based COW protocol for QKD in the telecom wavelength (1550 nm) where the
attenuation in the optical fiber is minimum. A laser of 1550 nm wavelength,
attenuator and intensity modulator is used for the generation of pulses having
average photon number 0.5 and repetition rate of 500 MHz. The experiment is
performed over 40 km, 80 km and 120 km of optical fiber and several
experimental parameters like disclose rate, compression ratio, dead time and
excess bias voltage of the detector are varied for all the cases (i.e., for 40
km, 80 km and 120 km distances) to observe their impact on the final key rate.
Specifically, It is observed that there is a linear increase in the key rate as
we decrease compression ratio or disclose rate. The key rate obtains its
maximum value for least permitted values of disclose rate, compression ratio
and dead time. It seems to remain stable for various values of excess bias
voltage. While changing various parameters, we have maintained the quantum bit
error rate (QBER) below 6%. The key rate obtained is also found to remain
stable over time. Experimental results obtained here are also compared with the
earlier realizations of the COW QKD protocol. Further, to emulate key rate at
intermediate distances and at a distance larger than 120 km, an attenuator of 5
dB loss is used which can be treated as equivalent to 25 km of the optical
fiber used in the present implementation. This has made the present
implementation equivalent to the realization of COW QKD upto 145 km.Comment: COW protocol for QKD is implemente
Can we control the amount of useful nonclassicality in a photon added hypergeometric state?
Non-Gaussianity inducing operations are studied in the recent past from
different perspectives. Here, we study the role of photon addition, a
non-Gaussianity inducing operation, in the enhancement of nonclassicality in a
finite dimensional quantum state, namely hypergeometric state with the help of
some quantifiers and measures of nonclassicality. We observed that measures to
characterize the quality of single photon source and anticlassicality lead to
the similar conclusion, i.e., to obtain the desired quantum features one has to
choose all the state parameters such that average photon numbers remains low.
Wigner logarithmic negativity of the photon added hypergeometric state and
concurrence of the two-mode entangled state generated at the output of a
beamsplitter from this state show that nonclassicality can be enhanced by
increasing the state parameter and photon number addition but decreasing the
dimension of the state. In principle, decreasing the dimension of the state is
analogous to holeburning and is thus expected to increase nonclassicality.
Further, the variation of Wigner function not only qualitatively illustrates
the same features as observed quantitatively through concurrence potential and
Wigner logarithimic negativity, but illustrate non-Gaussianity of the quantum
state as well.Comment: Quantification of nonclassicality enhancement due to photon addition
and holeburning in finite dimesional quantum stat
Quantum phase properties of photon added and subtracted displaced Fock states
Quantum phase properties of photon added and subtracted displaced Fock states
(and a set of quantum states which can be obtained as the limiting cases of
these states) are investigated from a number of perspectives, and it is shown
that the quantum phase properties are dependent on the quantum state
engineering operations performed. Specifically, the analytic expressions for
quantum phase distributions and angular distribution as well as measures of
quantum phase fluctuation and phase dispersion are obtained. The uniform phase
distribution of the initial Fock states is observed to be transformed by the
unitary operation (i.e., displacement operator) into non-Gaussian shape, except
for the initial vacuum state. It is observed that the phase distribution is
symmetric with respect to the phase of the displacement parameter and becomes
progressively narrower as its amplitude increases. The non-unitary (photon
addition/subtraction) operations make it even narrower in contrast to the Fock
parameter, which leads to broadness. The photon subtraction is observed to be a
more powerful quantum state engineering tool in comparison to the photon
addition. Further, one of the quantum phase fluctuation parameters is found to
reveal the existence of antibunching in both the engineered quantum states
under consideration. Finally, the relevance of the engineered quantum states in
the quantum phase estimation is also discussed, and photon added displaced Fock
state is shown to be preferable for the task.Comment: Quantum phase properties of an engineered quantum state has been
studied from various perspective
Lower- and higher-order nonclassical properties of photon added and subtracted displaced Fock states
Nonclassical properties of photon added and subtracted displaced Fock states
have been studied using various witnesses of lower- and higher-order
nonclassicality. Compact analytic expressions are obtained for the
nonclassicality witnesses. Using those expressions, it is established that
these states and the states that can be obtained as their limiting cases
(except coherent states) are highly nonclassical as they show the existence of
lower- and higher-order antibunching and sub-Poissonian photon statistics, in
addition to the nonclassical features revealed through the Mandel
parameter, zeros of Q function, Klyshko's criterion, and Agarwal-Tara
criterion. Further, some comparison between the nonclassicality of photon added
and subtracted displaced Fock states have been performed using witnesses of
nonclassicality. This has established that between the two types of
non-Gaussianity inducing operations (i.e., photon addition and subtraction)
used here, photon addition influences the nonclassical properties more
strongly. Further, optical designs for the generation of photon added and
subtracted displaced Fock states from squeezed vacuum state have also been
proposed.Comment: A comparative study of the nonclassicality present in photon added
and subtracted displaced Fock states shows photon addition is generally
preferable nonclassicality inducing operation, while subtraction also has
advantage in some cases over additio
Impact of photon addition and subtraction on nonclassical and phase properties of a displaced Fock state
Various nonclassical and quantum phase properties of photon added then
subtracted displaced Fock state have been examined systematically and
rigorously. Higher-order moments of the relevant bosonic operators are computed
to test the nonclassicality of the state of interest, which reduces to various
quantum states (having applications in quantum optics, metrology and
information processing) in different limits ranging from the coherent
(classical) state to the Fock (most nonclassical) states. The nonclassical
features are discussed using Klyshko's, Vogel's, and Agarwal-Tara's criteria as
well as the criteria of lower- and higher-order antibunching, sub-Poissonian
photon statistics and squeezing. In addition, phase distribution function and
quantum phase fluctuation have been studied. These properties are examined for
various combinations of number of photon addition and/or subtraction and Fock
parameter. The examination has revealed that photon addition generally improves
nonclassicality, and this advantage enhances for the large (small) values of
displacement parameter using photon subtraction (Fock parameter). The
higher-order sub-Poissonian photon statistics is only observed for the odd
orders. In general, higher-order nonclassicality criteria are found to detect
nonclassicality even in the cases when corresponding lower-order criteria
failed to do so. Photon subtraction is observed to induce squeezing, but only
large number of photon addition can be used to probe squeezing for large values
of displacement parameter. Further, photon subtraction is found to alter the
phase properties more than photon addition, while Fock parameter has an
opposite effect of the photon addition/subtraction. Finally, nonclassicality
and non-Gaussianity is also established using function.Comment: Nonclassical and quantum phase properties of photon added then
subtracted displaced Fock state are studied in detai
Manipulating nonclassicality via quantum state engineering processes: Vacuum filtration and single photon addition
The effect of two quantum state engineering processes that can be used to
burn hole at vacuum in the photon number distribution of quantum states of
radiation field are compared using various witnesses of lower- and higher-order
nonclassicality as well as a measure of nonclassicality. Specifically, the
witnesses of nonclassical properties due to the effect of vacuum state
filtration and a single photon addition on an even coherent state, binomial
state and Kerr state are investigated using the criteria of lower- and
higher-order antibunching, squeezing and sub-Poissonian photon statistics.
Further, the amount of nonclassicality present in these engineered quantum
states is quantified and analyzed by using an entanglement potential based on
linear entropy. It is observed that all the quantum states studied here are
highly nonclassical, and on many occasions the hole burning processes are found
to introduce/enhance nonclassical features. However, it is not true in general.
The investigation has further revealed that despite the fact that a hole at
vacuum implies a maximally nonclassical state (as far as Lee's nonclassical
depth is used as the quantitative measure of nonclassicality). However, any
particular process of hole burning at vacuum does not ensure the existence of a
particular nonclassical feature. Specifically,lower- and higher-order squeezing
are not observed for photon added even coherent state and vacuum filtered even
coherent state.Comment: Effect of holeburning is studied for various engineered quantum
state
Terminal hemimyelocystocele associated with Chiari II malformation
Terminal myelocystocele (TMC) results from failure of embryonic CSF to drain outside the neural tube creating CSF reservoir within a dorsal meningocele. Association of Chiari II malformation with diastematomyelia and myelocystocele is extremely rare. Myelocystoceles do not have neural tissue so they have good prognosis after treatment, however when associated with hydromelia and Chiari malformation they present with neurological deficits. We present details of a 2Â year old female who presented to us with this rare anomaly
Periodontal therapy in orthodontics- A case series
Interdisciplinary approach helps the specialists of contributing disciplines immensely in diagnosis, treatment planning, execution of planned treatment and problem solving for any untoward complication. Orthodontic treatment may be adjunctive to periodontal therapy or vice versa. Periodontal problems might lead to occlusal abnormalities which may require orthodontic correction. Also orthodontic treatment of adult patients is most frequently just one component of a more complex treatment involving several dental disciplines. Various orthodontic treatments also may precipitate some periodontal problems which frequently require periodontal management. This report discusses, through representative cases, potential periodontal problems and their management encountered before, during and after orthodontic treatment