Long Live The Qubit

Speaker: T.S. Mahesh (IISER, Pune, India)

Date and time


Qubit, or the fundamental unit of quantum information, can be realized by various two-level quantum systems. As we get closer to real-life applications of quantum information technologies, we will need better qubits and more of them. How long a qubit sustains classical/quantum memory against environmental influences is commonly characterized by T1 and T2 time constants. Due to the internal cancellation of errors, the singlet state (S0 state) of a pair of physical qubits, a zero-total-angular momentum state, is least susceptible to common noises. Using nuclear magnetic resonance (NMR) methods, we can initialize a pair of nearly equivalent nuclear spin qubits into a long-lived singlet state (LLS) with lifetimes far exceeding T1 and T2 barriers. LLS offers several exciting applications in spectroscopy, sensing, imaging, etc. [1]. The levels S0 and T0 (one of the triplet states) form a logical qubit with long-lived coherence (LLC). After briefly reviewing quantum control methods to prepare, store, harness, and readout LLS and LLC, I will describe some of our recent experiments [2,3] and point out future directions.


1. Long-Lived Singlet State: From NMR quantum information perspectives, T S Mahesh and Deepak Khurana, Book chapter in "Long-Lived Nuclear Spin Order" edited by Giuseppe Pileio, published by Royal Society of Chemistry (2020).

2. Counterdiabatic driving for long-lived singlet state preparation, Abhinav Suresh, Vishal Varma, Priya Batra, and T S Mahesh, J. Chem. Phys. 159, 024202 (2023).

3. Long-lived singlet state in oriented phase and its survival across the phase transition into isotropic phase, Vishal Varma and T S Mahesh, Phys. Rev. Appl. 20, 034030 (2023) [Editor Suggested].

T.S. Mahesh

T. S. Mahesh completed his bachelor's degree from JCBM College, Sringeri, Karnataka, and his master's degree from Mangalore University, Karnataka. After completing his PhD from the Department of Physics, IISc, Bangalore, he did postdoctoral research at MIT Cambridge, USA, and subsequently at the University of Dortmund, Germany. Since 2007, he has been a faculty member of Physics at IISER Pune. His research group at IISER Pune explores the quantum world via magnetic resonance. Spins, the quantum particles with spin-angular momentum, behave like tiny magnets and precess in a magnetic field. Nuclear spin ensembles in a bulk sample dance to the tune of radio waves and can be studied via nuclear magnetic resonance (NMR). Single spins can often be studied via optically detected magnetic resonance (ODMR). Using magnetic resonance, they study quantum information, quantum control, quantum computing, quantum simulations, quantum many-body effects, and quantum foundation.