Colloquium
Long Live The Qubit
Speaker: T.S. Mahesh (IISER, Pune, India)
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.
References:
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].
