Research: My research is based on Nuclear Magnetic Resonance(NMR) phenomenon, where an ensemble of spin 1/2 nuclei under the static magnetic field can be controlled using electromagnetic waves close to their resonance frequency. NMR is used as a tool to carry out experimental research and study of Quantum Computing and Information Processing. Quantum computing exploits the quantum laws of the nature which  gives us an advantage over classical computers to perform certain task efficiently.  The spin 1/2 nuclei is acting as a qubit which is a basic unit of Quantum computing.

 Algorithmic cooling: The population difference between the upper and lower spin state of a qubit is called polarization and it follows Boltzmann's distribution at room temperature. This small difference in population is responsible for the signal we get in NMR.  But, this polarization depends on the Gyromagnetic ratio of a particular nuclei of interest. My goal is to increase the polarization of  low Gyromagnetic ratio nuclei viz. 13C and 15N. This can be achieved by using Algorithmic cooling protocol that uses concepts from information processing to increase the polarization of a nuclei of our interest.  This method manipulates the density matrix such that the entropy from our qubit of interest can be pumped to other qubits in our system. It leads to decrease in the entropy of our qubit of interest and grows the population difference.  This enhanced polarization can be noticed as an amplification in the signal-to-noise ratio after using the cooling protocol.

Quantum heat engine and fluctuation theorem: Developement in Quantum Thermodynamics has lead to discovery of many theoretical predictions about the working of quantum heat engine and fluctuation in their average work and absorbed heat. These fluctuation theorems evaluates the working of systems when they are driven to nonequilibrium state. Quantifying these quantum and thermal fluctuation at microscopic level system is crucial for fundamental and practical understanding. We have implemented a 2 stroke(SWAP) quantum heat engine using a 2 qubit liquid NMR quantum processor. This engine has been used as a prototype to verify a fluctuation theorem, which relates the work done and heat absorbed by a quantum heat engine to its initial spin temperature of qubits. This verified fluctuation theorem can be regarded as generalization of Second law of thermodynamics. We have also observed the working of 2 stroke heat engine as heat engine and refrigerator which depends on the initial spin temperature of qubits and the energy gap between them.

Study of nonequilibrium thermodynamics: When any quantum state at equilibrium is driven out of equilibrium via an external driving agent the change in relative entropy is non-zero. This irreversible entropy can be divided into coherent and incoherent part. Coherent part is coming due to the production of coherence in the system after the external unitary driving  and incoherent part is due to the undesirable transition(or more accurately, population mismatch between desired state and actual state). We have experimentally seperated both these part of the irreversible entropy and quantified the produced entropy and the coherence in the system. The nonequilibrium entropy production for an externally driven system is larger than the bures length, the geometric distance between the actual state and the desired state. 

Shortcut to adiabaticity in quantum otto heat engine: Heat engines has been at the backbone of the industrial revolution since its discovery by Carnot, it converts heat into a useful work which can be used to drive many modern mechanical machine.  Since, the real engine have a finite operation cycle time, therefore they are not in an exact equilibrium state during operation to satisfy quasistatic process condition. Technological developement has facilitated us to experimentally explore the thermodynamics in quantum domain. Hence, The finite time operation of quantum otto engine leads to a trade-off between efficiency and output power . If we increase the cycle time which increases efficiency but decrease in power and vice versa. This trade-off caveat can be bypassed by using shortcut-to-adiabaticity protocol. We have experimentally implemented a quantum otto heat engine using spin 1/2 nuclei as working system in a NMR quantum processor. We investigate its performance using shortcut-to-adiabaticity technique via counderdiabatic driving with the inclusion of the cost to perform shortcut. We have found significant improvement in the performance of engine driven by shortcut-to-adiabaticity as compared to non adiabatic engine.