Research Projects

The last three decades have witnessed the advancement of quantum technology in the form of quantum devices designed using quantum principles for a variety of purposes. Arguably, the most prominent among these devices are the quantum computers, quantum communication devices and small-scale quantum appliances which include quantum thermal machines, and quantum sensors. It has been realized that having a large number of qubits in these devices for achieving “quantum supremacy” is necessary. Efforts towards achieving this have already produced noisy intermediate-scale quantum (NISQ) devices made of 50–100 qubits. These NISQ devices are now being tested for different quantum tasks including hosting good quality logical qubits, which are the stepping stones towards realizing the envisioned large-scale quantum computers. The models describing these multi-qubit systems are designed by arranging qubits on lattices of special geometry, where large quantum states, referred to as the stabilizer states, serve as resources. Apart from these large quantum systems, the need for miniaturization of machines has also been in focus, especially to understand the laws of thermodynamics and the relevant thermodynamic quantities at the quantum level. So far, quantum thermal machines that have been extensively investigated are (1) refrigerators, (2) batteries, (3) transistors, and (4) diodes, where interacting multi-qubit systems have been used as working mediums. . Large or small, the widely accepted figures of merit for the quantum states occurring in the systems serving as platforms for different quantum machines are the different correlations, such as entanglement, quantum discord and related measures, and coherence. These quantum correlations are of purely quantum origin, and have no classical analogue. However, characterizing quantum machines using such quantum correlations may prove to be difficult due to a number of challenges, even for a device of few qubits because of the resource intensive state readout protocols, as well as due to the presence of noise, which forces one to compute quantum correlations in a mixed state of a large system. Moreover, in a realistic scenario where noise is present, specific operations required to be made on the quantum state for the quantification of the quantum correlations may also be noisy. However, the implication of this realistic modification in the protocol for quantifying quantum correlations on the understanding of these quantum machines is not clear yet, which is the aim for our current project. It originates from the practical motivation of appropriately modifying the operations required in the protocol for quantifying quantum correlations due to possible imperfections in the performed operation. It also aims to subsequently test the results of these modifications in quantum devices, including quantum thermal machines and quantum codes.