Alladi Ramakrishnan Hall

The promising world of quantum measurements: Weak measurements, inherent information loss, reverse quantum measurements and measurements in and with relativistic effects

Shrobona Bagchi

Center for Quantum Information, Korea Institute of Science and Technology, Seoul, Korea

In this talk, I elucidate my research works
on the topic of quantum measurements. The different kinds of quantum
measurements that are presented in this talk are the single weak
measurements, continuous weak measurements and the reverse quantum
measurements in two different contexts. The two different contexts are the
foundational quantum mechanics as well as the quantum technological
applications. In the quantum technological context, we explore the role of
continuous weak measurements in the protocol of quantum state smoothing,
which is an advanced version of quantum state estimation protocol. In this
context we also show how a prediction-retro-diction kind of measurement can
be applied to improve the quantum state smoothing protocol efficiency. In
the next topic, I will talk about the application of weak quantum
measurements in the quantum foundations context, specifically in the
application of the quantum pigeonhole principle. In our work on this topic,
we show that in the mathematical framework of quantum theory, the classical
pigeonhole principle can be violated more directly than previously
suggested. This is a setting closer to the traditional statement of the
principle. We analyze the experiments done on this topic and after
identifying the drawbacks of recent experiments of the previous version of
the quantum pigeonhole effect, we argue that a definitive experimental
violation of this type of pigeonhole principle is still required and
propose such an implementation using modern quantum computing hardware: a
superconducting circuit with transmon qubits. We then move on to another
discussion regarding the quantum measurements in the relativistic scenario.
On this foundational question, we show that relativistic effects are needed
to be involved in the quantum measurements for its complete description. We
also point out that this will be useful in future space based quantum
technologies.