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Publications and source records attributed to Dipankar Home.

63 records · Page 4Linked to original sources
arXiv2006

Observability of the arrival time distribution using spin-rotator as a quantum clock

An experimentally realizable scheme is formulated which can test any postulated quantum mechanical approach for calculating the arrival time distribution. This is specifically illustrated by using the modulus of the probability current density for calculating the arrival time distribution of spin-1/2 neutral particles at the exit point of a spin-rotator(SR) which contains a constant magnetic field. Such a calculated time distribution is then used for evaluating the distribution of spin orientations along different directions for these particles emerging from the SR. Based on this, the result of spin measurement along any arbitrary direction for such an ensemble is predicted.

quant-ph↗
arXiv2006

On the quantum analogue of Galileo's leaning tower experiment

The quantum analogue of Galileo's leaning tower experiment is revisited using wave packets evolving under the gravitational potential. We first calculate the position detection probabilities for particles projected upwards against gravity around the classical turning point and also around the point of initial projection, which exhibit mass dependence at both these points. We then compute the mean arrival time of freely falling particles using the quantum probability current, which also turns out to be mass dependent. The mass dependence of both the position detection probabilities and the mean arrival time vanish in the limit of large mass. Thus, compatibility between the weak equivalence principle and quantum mechanics is recovered in the macroscopic limit of the latter.

quant-ph↗
arXiv2002

Understanding Quantum Superarrivals using the Bohmian model

We investigate the orgin of ``quantum superarrivals'' in the reflection and transmission probabilities of a Gaussian wave packet for a rectangular potential barrier while it is perturbed by either reducing or increasing its height. There exists a finite time interval during which the probability of reflection is {\it larger} (superarrivals) while the barrier is {\it lowered} compared to the unperturbed case. Similarly, during a certain interval of time, the probability of transmission while the barrier is {\it raised} {\it exceeds} that for free propagation. We compute {\it particle trajectories} using the Bohmian model of quantum mechanics in order to understand {\it how} this phenomenon of superarrivals occurs.

quant-ph↗
arXiv2001

Ipso-information-transfer

A tripartite system with entangled non-orthogonal states is used to transfer retrievable or usable information without requiring an external channel, ipso-information-transfer (IIT). The non-Schmidt decomposable entanglement couples two independent interactions through which the information is transferred between a pair of non-interacting components of the system. We outline a dynamical model of IIT using localised particles. Implications for quantum nonlocality are raised.

quant-ph↗
arXiv2001

Bell's inequality for a single spin 1/2 particle and quantum contextuality

We argue that for a \emph{single particle} Bell's inequality is a consequence of noncontextuality and is \emph{incompatible} with statistical predictions of quantum mechanics. Thus noncontextual models can be empirically falsified, \emph{independent} of locality condition. For this an appropriate entanglement between \emph{disjoint} Hilbert spaces pertaining to translational and spin degrees of freedom of a single spin-1/2 particle is invoked

quant-ph↗
arXiv2000

Does nonorthogonality necessarily imply nonmaximal entanglement ?

We show that bipartite entanglements involving non-orthogonal states are {\it necessarily nonmaximally} entangled, however {\it small} the non-orthogonality may be. How the deviation from maximal entanglement is related to nonorthogonality is quantified by using two independent measures of entanglement corresponding to the violation of Bell's inequality and the entropy measure respectively. This result is true even if one of the subsystems has orthogonal states. An application of this is that a maximal violation of Bell's inequality in entangled neutral kaons is not possible in the presence of CP violation.

quant-ph↗
arXiv1999

Barrier Perturbation Induced Superarrivals and Nonlocality in a Time-Evolving Wave Packet

We compute the time evolving probability of a Gaussian wave packet to be reflected from a rectangular potential barrier which is perturbed by reducing its height. A time interval is found during which this probability of reflection is enhanced (superarrivals) compared to the unperturbed case. Such a time evolving reflection probability implies that the effect of perturbation propagates across the wave packet faster than its group velocity - a curious form of nonlocality.

quant-ph↗
arXiv1999

Determination of When an Outcome is Actualised in a Quantum Measurement using DNA - Photolyase System

The biochemical attachment of photolyase to ultraviolet (uv) absorbed DNA molecules provides a method for registering whether a source has emitted photons. Here using laws of chemical kinetics and related experimental methods we argue that the instant after which this information becomes discernible can be empirically determined by retrodicting from relevant data when the photolyase binding to uv-absorbed DNA molecules has started occuring. Thus an empirically investigable twist is provided to the quantum measurement problem.

quant-ph↗