Since 1980s, Dipankar Home has been working on various Foundational aspects of Quantum Mechanics, especially on topics related to Quantum Entanglement, Quantum Nonlocality, the Quantum Measurement Problem, the Quantum Zeno Effect, the Quantum Time Distributions, and on the Nonstandard Interpretations of Quantum Mechanics such as the Bohmian model. Of late, Home has also been working on issues concerning Quantum Information Transfer/Processing, such as Quantum Teleportation and Quantum Cryptography.
The thrust area of Home’s research works has been to probe the way the abstract conceptual issues underpinning Quantum Mechanics can be linked to experiments in order to derive new insights and uncover some of the unexplored implications of Quantum Mechanics. Among the research contributions by Home, two of his proposed experiments have already been realized in practice:
(i) One of these by Home and his collaborators (Bell's Inequality for a Single Spin 1/2 Particle and Quantum Contextuality; with S. Basu, G. Kar and S. Bandyopadhyay, Physics Letters A 279, 281 (2001)) gave a novel formulation of a Bell-like inequality for a single particle so that an incompatibility between Quantum Mechanics and the hypothesis of noncontextuality (the notion that an individual outcome of a measurement of a dynamical variable does not depend on the specifics of an experimental context) can be experimentally tested. Earlier, there have been a number of mathematical theorems on this issue, but no experimental test was possible. The scheme proposed by Home et al. was the first to indicate the feasibility of experimentally testing the property of contextuality in Quantum Mechanics by entangling the “path” and “spin” – type degrees of freedom of a single particle.
Subsequently, an experiment using neutrons based on the above scheme was carried out by H. Rauch and Y. Hasegawa at Atominstitut, Vienna; this is the first experiment showing the violation of a Bell-like inequality for a single particle, implying Quantum Contextuality; published in Nature 425, 45 (2003), followed by related studies pulished in J. Opt. B 6, S7 – S12 (2004);Physica B 385, 1377 (2006), Physical Review Letters 100, 130404 (2008) A similar experiment was also done, using photons, by M. Michler et al.; Physical Review Letters 84, 5457 (2000).
(ii) The other proposal by Home that has been empirically tested is the one with P. Ghose and G. S. Agarwal which formulated a scheme that used the predicted quantum tunneling of single photon states of light to show both “wave” and “particle” – like properties of a single photon state in the same experimental arrangement (An Experiment to throw more Light on Light; with P. Ghose and G. S. Agarwal, Physics Letters A, 153, 403 (1991); 168, 95 (1992)). This proposal provoked debate about Bohr’s famous Complementarity Principle which decrees mutual exclusiveness between “wave” and “particle” properties of quantum objects.
The experiment suggested by Home and his collaborators was subsequently performed by Y. Mizobuchi and Y. Ohtake at the Hamamatsu Photonics Central Research Laboratory, Japan (Y. Mizobuchi and Y. Ohtake, Physics Letters A 168, 1 (1992)), and the results confirmed the theoretical prediction by Home and his collaborators. Another recent experiment has also confirmed this predicted effect (G. Bridaa, M. Genovesea , , M. Gramegnaa and E. Predazzi, bPhysics Letters A 328 313 (2004)).
Two other works by Home currently await experimental realization:
(a) The question of having efficient resources of entangled states is of considerable importance because Quantum Entanglement lies at the heart of not only the foundational issues of Quantum Mechanics like Quantum Nonlocality, and the Quantum Measurement Problem, but is also at the core of the development of new Quantum Technologies like Cryptography and Teleportation. However, to date all the experimental schemes available for this purpose are system-specific, and most empirical studies have been done using photons.
Against this backdrop, an entirely new approach to have a generic resource for preparing entangled states of any system (Bosons, Fermions or Macromolecules) has been formulated and its implications have been studied (Generic Entanglement Generation, Quantum Statistics, and Complementarity; with S. Bose, Physical Review Letters 88, 050401 (2002); Testing Quantum Statistics with Particles in Distinguishable States; with S. Bose, International Journal of Quantum Information 3, 117 (2005)). The proposed scheme uses the intrinsic property of “indistinguishability” of identical quantum objects originating from independent sources. This novel technique of linking Quantum Entanglement with Quantum Statistics is experimentally implementable, and it also suggests a number of hitherto unexplored implications, including the possibility of teleporting states of massive objects.
(b) An experimentally realizable scheme has been formulated (Observability of the arrival time distribution using spin-rotator as quantum clock; with Alok Kumar Pan and Md. Manirul Ali, Physics Letters A 352, 296 (2006)) which can test any postulated quantum mechanical approach for calculating the transit/arrival time distribution whose quantum prediction has an intrinsic nonuniqueness. This proposed scheme is in terms of the transit/arrival time distribution of spin-1/2 neutral particles corresponding to a Gaussian wave packet passing through a spin-rotator (SR) which contains constant magnetic field. Such a calculated time distribution can then be used for evaluating the distribution of spin orientations for the particles emerging from the SR. Based on this, the result of spin measurement along any arbitrary direction can be predicted that is empirically testable. Thus, our suggested setup enables experimental discrimination between different quantum approaches available for computing the transit/arrival time distribution.time distribution.
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