New Study Can Help Control Noise in Quantum Technology

A new study by Bangalore-based scientists has shed new light on how a charged particle in contact with an environment behaves in the presence of a magnetic field when subjected to ultra-cold temperatures.

Control noise

Scientists involved in the study have said that the latest findings could deepen existing knowledge and explore ways to control noise in the domain of quantum technology.

Quantum technology is too vulnerable to disturbances in the environment that corrupt information stored in quantum computers, so understanding the role of noise in quantum technology and finding ways to control it has long been a challenge for scientists.

Physicists from the Raman Research Institute (RRI), an autonomous institute funded by the Government’s Department of Science and Technology from India, and TIFR – International Center for Theoretical Sciences (ICTS), investigated the role of noise in quantum technology and the evolving area called quantum Brownian motion. They discovered how noise in the quantum domain can affect a charged particle in a magnetic field and traced the role of quantum noise in decomposing correlations at ultracold temperatures in the context of a charged particle in a magnetic field in a recently published journal Physics A.

Fundamental building

Brownian motion, the random motion of particles when suspended in a fluid, forms one of the fundamental building blocks of physics, thanks to Albert Einstein’s seminal work in this area. Quantum Brownian motion is a class of dynamics possible for a continuous, open quantum degree of freedom.

In the past, researchers have studied the behavior of a neutral Brownian particle in a similar context. However, the researchers said that a theoretical study involving the slow late dynamics of a charged Brownian particle in an applicable magnetic field at ultra-cold temperatures is a first.

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The study makes predictions about the nature of the decay of factors called position correlation function, position-velocity correlation function, and velocity autocorrelation function in the quantum domain accessible through experiments with ultracold atoms. The predictions can be tested by considering a charged particle in a magnetic field at ultra-cold temperatures (on the order of a few nano Kelvin) in an optical molasses that mimics a viscous environment.

Domain of high temperatures

“In the classical domain of high temperatures, the correlations decay very quickly over long times. On the contrary, in the low temperature domain, the decomposition of the correlations slows down considerably. We study how the magnetic field and harmonic oscillator trap particle confinement and affect the decay of correlations in the low-temperature quantum domain,” said Professor Supurna Sinha, a member of the Theoretical Physics faculty and one of the co-authors of the article entitled ‘Long tails in the quantum Brownian motion of a charged particle in a magnetic field’.

While the strength of the magnetic field affects the amplitude of the decay, it slows down when quantum fluctuations dominate over thermal fluctuations, said Suraka Bhattacharjee, an RRI postdoctoral fellow and lead author of the paper.

This work is an excellent example of cross-thematic research at RRI, in this case between theorists and experimenters from the Quantum Mixtures lab, part of RRI’s group of Quantum Labs.

Continuing theoretical work along similar lines, this group is currently trying to understand the behavior of a quantum brownian particle with spin, the study of which is ongoing.