Proposal to use spintronic devices for weak-value quantum metrology

Abstract: Using quantum transport theory, we propose viable spintronic device platforms for solid-state implementations of the tunnel time estimator [1] and ultimately a new platform for quantum metrology [2]. The tunneling time problem – the question on how long a particle spends inside a forbidden region, has puzzled physicists since the inception of quantum mechanics. Following recent ground-breaking experiments using cold atoms [3,4], this topic that innately involves quantum weak values and connections with generalized von Neumann measurements [5], which we show can be distilled and exploited from magnetoresistance measurements.

Starting from the basics of quantum device theory using the Keldysh non-equilibrium Green’s function (NEGF) approach, we will present a solid-state implementation of the Larmor clock [1] that exploits tunnel magnetoresistance to “distill” information on how long itinerant spins take to traverse a barrier embedded in it. We provide a direct mapping between the magnetoresistance signals and the tunneling times that aligns well with the interpretation in terms of generalized quantum measurements and quantum weak values [5].

Moving on to quantum metrology, it is known that quantum weak-values can potentially effectuate parameter estimation with an ultra-high sensitivity and has been typically explored across quantum optics setups. Recognizing the importance of sensitive parameter estimation in the solid-state, we propose a spintronic device platform [2] to realize this. The setup estimates a very weak localized Zeeman splitting by exploiting a Fabry-Perot resonant tunneling enhanced magnetoresistance readout. These results put forth definitive possibilities in harnessing the inherent sensitivity of resonant tunneling for solid-state quantum metrology with potential applications, especially, in the sensitive detection of small induced Zeeman effects in quantum material heterostructures.

Our ideas can be further generalized for applications involving quantum weak values, with many possibilities that can be envisioned using the emerging properties of quantum materials.

REFERENCES

1. A. Mathew, K. Y. Camsari and B. Muralidharan, Phys. Rev. B, 105, 144418, (2022).
2. M Subramanian, A. Mathew and B. Muralidharan, ArXiv: 2211.17060, (2022) [In Revision]
3. R. Ramos et.al., Nature, 583,529, (2020).
4. D. C. Spierings and A. M. Steinberg, Phys. Rev. Lett., 127, 133001, (2021).
5. A. M. Steinberg, Phys. Rev. Lett., 74, 2405, (1995).

BIO OF THE SPEAKER: Prof. Bhaskaran Muralidharan obtained his B.Tech in Engineering Physics from the Indian Institute of technology (IIT) Bombay in 2001, his M. S. and Ph. D in Electrical Engineering from Purdue University, West Lafayette, USA in 2003 and 2008 respectively. Between 2008-2012, he was a post-doctoral associate at the Massachusetts Institute of Technology (MIT) and at the Institute for theoretical Physics at the University of Regensburg, Germany.  Since 2012, he has been a faculty in the Department of Electrical Engineering at IIT Bombay, where he is currently a Professor. His core research area is computational quantum transport and its applications to modeling and simulation of “Beyond Moore” devices. His research output spans diverse areas of emerging nanoscale devices, ultimately built on top of a broad and fundamental foundation of utilizing quantum transport for novel functionalities. He was also the recipient of the APS-IUSSTF professorship award in 2014, the Shastri Indo-Canada fellowship 2019 and the SERB-STAR award in 2019. He is a recipient of the Excellence in Teaching Award in IIT Bombay. He is an Associate Editor in the IEEE Transactions on Nanotechnology, on the Editorial board of Scientific Reports and Materials for Quantum Technology (IOP). He has also been a regular visiting Professor at the Institute for Quantum Computing (IQC) in the University of Waterloo, Canada.