## Supriyo Datta

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### Overview

**Supriyo Datta**

**Thomas Duncan Distinguished Professor of Electrical and Computer Engineering**

School of Electrical Engineering, Purdue University

465 Northwestern Avenue, West Lafayette, Indiana 47907-1971

We have tried to convey our research to a broad multidisciplinary audience through books and online courses

**Current Research**

We have always been intrigued by Feynman’s (*Int. J. Theor. Phys.* **21**, 1982) observation that

“ The only difference between a probabilistic classical world and the equations of the quantum world is that somehow or other it appears as if the probabilities would have to go ** negative** .. “

The awesome power of quantum computing comes from exploiting these negative (more generally complex) probabilities, which in turn requires stringent experimental conditions to protect the phase.

A probabilistic computer by contrast can be built with existing technology to operate at room temperature to provide a benchmark for quantum computing. Which algorithms can and cannot be implemented without the magic of complex probabilities?

With this question in mind, our group has introduced the concept of a ** p-bit** that is intermediate between the

**of digital computing and the**

*bits***of quantum computing. See for example,**

*qubits*An FPGA emulation *IEEE Access*

An experimental demonstration *Nature*

A popular description *IEEE Spectrum*

*We are using this approach to accelerate a wide variety of problems including Bayesian networks, optimization, Ising models, quantum Monte Carlo, to name a few.*

Related online course: *Boltzmann Law: Physics to Computing * (nanoHUB-U) , *(edX) *

**Past Research**

We have tried to distill the essence of past research for a broad multidisciplinary audience through books and online courses as indicated.

* 1. Surface Acoustic Waves: *As a graduate student, Datta started his career in ultrasonics working on the scattering of surface acoustic waves in piezoelectric crystals. His work in this area is described in his book

- S. Datta,
*Surface Acoustic Wave Devices,*Prentice-Hall, 1986

* 2. Spintronics: *After joining Purdue as a faculty member, Datta started work on current flow in electronic devices and how it is affected by the wave nature of electrons. This is described in his book

• S.Datta, *Quantum Phenomena*, Addison-Wesley, 1989

and it led him to the proposal in 1990 to use a relativistic effect known as spin-orbit coupling to manipulate electronic spin with an electric field instead of a magnetic field. This proposal was experimentally demonstrated seven years later, and the *electrical control of spin* is now well-established and constitutes an integral part of the thriving field of spintronics. A recent perspective looking back at this work

• S. Datta, *How we proposed the spin transistor*, Nature Electronics, **1**, 604 (2018)

* 3. Mesoscopic Physics: *Next his group combined the non-equilibrium Green function (NEGF) method of many-body physics and the Landauer approach of mesoscopic physics, starting with the paper

This work is described in

- S. Datta,
*Electronic Transport in Mesoscopic Systems (Cambridge 1995)*

* 4. NEGF Method: *The NEGF method was then combined with an atomistic Hamiltonian to provide a comprehensive conceptual and computational framework for quantum transport, for which Datta was elected to the NAE.

- S. Datta,
*Quantum Transport: Atom to Transistor (Cambridge 2005)*

This approach is now a part of the simulation tools used by semiconductor chip manufacturers to design nanotransistors, billions of which go into every chip.

Related online course: *Introduction to Quantum Transport *(nanoHUB-U) , *(edX)*

- A short lecture: NEGF: A New perspective

* 5. Molecular Electronics: *The work on quantum transport also brought together two distinct communities, device physicists and quantum chemists, enabling a cross-fertilization of ideas, see for example, Current-voltage characteristics of self-assembled monolayers.

This work also led to an interesting prediction in 2003, which was experimentally demonstrated in 2007, launching the field of molecular thermoelectricity.

* 6. New Perspective on Current Flow:* Subsequently, his group used the insights from nanoelectronics to provide an elegant view of current flow in large conductors:

- S. Datta,
*Lessons from Nanoelectronics: A New Perspective on Transport*,*World Scientific 2012, 2*^{nd}Edition 2017

Related online course: *Fundamentals of Current Flow *(nanoHUB-U) , *(edX)*

This work led to a modular approach to the analysis of spin-based circuits.

It also led to a different view of spin-charge conversion in spin-orbit materials, predicting new results some of which have been experimentally confirmed.

* 7. Negative Capacitance Devices:* A potentially far-reaching contribution is the proposal to stabilize materials in an unnatural negative capacitance state and use it to reduce the operating voltage of nanotransistors. The proposal was so far outside the mainstream that it met with considerable skepticism from experts, but is now considered a prime candidate for reducing dissipation in nanotransistors and extending Moore’s Law.