New test with quantum coins & computers for quantum sensing

Researchers from Raman Research Institute (RRI), an autonomous institution under the Department of Science & Technology, have devised a new test for fairness of quantum coin or ‘qubit’ (the basic unit of information in a quantum computer) using entanglement theory.

Significance: This is a significant contribution to quantum state discrimination, an essential aspect of quantum information science which is expected to influence quantum sensing. The new test uses entanglement to test the fairness of the quantum coin.

Entanglement: Entanglement is a special type of correlation that exists in the quantum world with no classical counterpart. The researchers from RRI made use of this quantum resource to arrive at a test for fairness of a quantum coin (a qubit). Their strategy, which makes use of entanglement, enables better discrimination between quantum states. Such advantage is valuable in quantum sensors.

The work is appearing in Pramana, the Journal Of Physics and a related paper has appeared in the International Journal of Quantum Information.

This work is a significant contribution to the domain of quantum state discrimination, which is an essential aspect of quantum information science. It brings out the crucial role of entanglement in improving our ability to discriminate quantum states.

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. Given a string of qubits representing a series of trials, one can measure them individually and determine the state with a certain confidence. The team has shown that there is an improved strategy which measures the qubits after entangling them, which leads to a greater confidence.

In their exploration the researchers used a variety of tools: analytical techniques, numerics and computer simulation and experiments on the IBM quantum computing facility. All these tools were used collectively to arrive at an understanding of the role of entanglement in quantum state discrimination.