Articles written in Pramana – Journal of Physics
Volume 48 Issue 5 May 1997 pp 969-975
Thomas rotation and polarized light: A non-abelian geometric phase in optics
We describe a
Volume 94 All articles Published: 15 March 2020 Article ID 0057 Rapid communication
Likelihood theory in a quantum world: Tests with quantum coins and computers
ARPITA MAITRA JOSEPH SAMUEL SUPURNA SINHA
By repeated trials, one can determine the fairness of a classical coin with a confidence which grows with the number of trials. A quantum coin can be in a superposition of heads and tails and its state is most generally a density matrix. Given a string of qubits representing a series of trials, one can measure them individually and determine the state with a certain confidence.We show that there is an improved strategy which measures the qubits after entangling them, which leads to a greater confidence. This strategy is demonstrated on the simulation facility of IBM quantum computers.
Volume 96 All articles Published: 3 March 2022 Article ID 0053 Research Article
Quantum Langevin dynamics of a charged particle in a magnetic field: Response function, position–velocity and velocity autocorrelation functions
SURAKA BHATTACHARJEE URBASHI SATPATHI SUPURNA SINHA
We use the quantum Langevin equation as a starting point to study the response function, the position– velocity correlation function and the velocity autocorrelation function of a charged quantum Brownian particle in the presence of a magnetic field and linearly coupled to a heat bath via position coordinate. We study two bath models – the Ohmic bath model and the Drude bath model and make a detailed comparison in various time–temperature regimes. For both bath models, there is a competition between the cyclotron frequency and the viscous damping rate giving rise to a transition from an oscillatory to a monotonic behaviour as the damping rate is increased. In the zero point fluctuation dominated low-temperature regime, non-trivial noise correlations lead to some interesting features in this transition. We study the role of the memory time-scale which comes into play in the Drude modeland study the effect of this additional time-scale. We discuss the experimental implications of our analysis in the context of experiments in cold ions.
Volume 97, 2023
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