AMA with Prof. Sai

"Ask Me Anything!" with Prof. Sai Vinjanampathy

Research Interests:

I am interested in understanding quantum physics and applying it to future quantum technologies. Though many of you have heard of quantum computers, the areas of future technology where quantum mechanics can make a difference are numerous. What physicists are doing now in this emergent technology area is to chalk out what the physics of these devices should be such that they outperform their classical counterparts.

I divide this research interest into three broad areas: quantum information theory (QIT), quantum control theory (QCT) and quantum thermodynamics (QTh). I currently teach a course in QIT in the department, so I presume not much introduction is needed for this topic. In QIT, I am currently mainly interested in measuring and characterising memory (non-Markovianity) in quantum systems.

In QCT, I work on a variety of problems related to realistic experimental design, trying to design faster, more efficient and practical gates for given quantum computing architectures (ex: quantum dots, superconducting devices, etc). This is an important problem since it will assist our experimental colleagues in the department and elsewhere with quantum computers that have been optimised to combat the deleterious effects of the environment they sit in (like the damping of a pendulum due to collisions with air molecules). I am currently trying to use machine learning techniques, numerical optimisation and variational principles to work on these designs.

My third interest is in QTh, which can technically be described as non-equilibrium quantum statistical mechanics from a quantum information theoretic standpoint (I confess this is a mouthful). For example, consider energy storage devices. Should batteries be made of classical particles (which is to say, individual spins, where you only consider that the spin can be "up" or "down", but not in superposition) or quantum (where you exploit superposition, entanglement and other quintessentially quantum mechanical properties)? I ask and answer such questions and apply them to make machines with thermal analogues ("quantum" engines, batteries, fridges, etc) which surpass their classical counterparts and hence can be candidates for future quantum technology.

Employment:

2016-Present: Assistant Professor, Indian Institute of Technology Bombay.

2016-Present: Visiting Research Fellow, Centre for Quantum Technologies, National University of Singapore.

2012-2016: Postdoctoral Fellow, Centre for Quantum Technologies, National University of Singapore.

2010-2012: Postdoctoral Fellow, Department of Physics, University of Massachusetts Boston.

Education:

2010: Doctor of Philosophy Physics & Astronomy, Louisiana State University,USA.

2004: Master of Science Physics, Indian Institute of Technology Madras, India.

2002: Bachelor of Science Physics, Madras University, India.

Questions and Answers:

Why do you keep the lights turned off in you room?

Its a childhood habit that helps me focus. I have a table lamp for when I need to read/write and the computers for other times. I turn the lights on if anyone steps into my office, since often the discussions that follow happen on the blackboard.

What is the single significant problem that is being explored in quantum thermodynamics, other than curiosity driven research in quantum systems?

In quantum thermodynamics, just like in quantum tech, its all about leveraging quantum mechanical advantage and combine it with thermodynamics. A few problems I think would attract major attention if made practical are small quantum engines, machines that convert heat into entanglement and coherence, quantum batteries that can move energy faster than classical batteries and a "compact" quantum fridges.

How do you maintain that magnificent beard? Is it wax or is it natural?

Just the great barbers at y-point.

How doth thee killeth thy time?

I love cooking and enjoy playing squash.

Can you trace back to any incident which cemented your interest in Physics?

Well, my father was a physicist, who inspired both my sister and myself to do physics. Besides this "home field introduction", there were a series of lectures by G.Rajashekharan (IMSc, Chennai) on the eve of the Indian neutrino project I attended as an undergrad. It was the first time I heard a theorist speak about physics and it was music to my ears. I joined IITM and followed several profs there, cementing this interest as it matured towards theoretical quantum optics and computing.

What do you think will be the next big thing in your field? How do you plan to be a part of it?

Next big thing (perhaps): quantum synchronisation and its applications in quantum technology. I think this topic is "big", since it has the effect of combining non-linearity with non-classicality. Think of solitons, feedback stabilisation and all of the other advantageous non-linear dynamical effects we have observed in classical mechanics. I am working in this area and have invested some of my time and resources towards this.
The next big Indian thing: The quantum computing effort at various experimental labs in India. To support this, I am investing in gate design and optimisation for these experimentalists.

What advice do you have for UGs and PGs?

Let me begin by warning against random advice. I am sure you get plenty of physics "gyan", so let me share personal maxims that are not specifically about physics. I am a bit irreverent towards "gyan", so I offer these words for you to consider and/or ignore.

Erase "fate" as a point of view from your life. Problems have solutions, but those solutions are predicated on you thinking that problems are solvable. Don't give up on things. I often see people accept defeat over their future before they have even tried anything.
Take a rational point of view of life. Be skeptical of everything.
Always listen to people you disagree with. If you are wrong, you get to clear your mind. If you are right, your arguments are sharpened by the opposition.

How do you remember names of so many scientists? Is it a deliberate attempt?

Its a bit of both. I just naturally remember names and references, but I also want to name people for various reasons:

To highlight who the authors are to encourage reading original sources.
So that students can seek these people out (QC being a young field, the leaders of the field are thankfully alive and well...I name names so that YOU can read their papers and talk to them, as opposed to just taking my word for anything...) and
To highlight those Indian physicists who are doing great work. This third point is important to me because I want our students, who are often great, to seek people in India who are doing great work for internships, Ph.D.s etc.

How far would you say, are we from a commercial working quantum computer?

Commercial: there is already one big company (DWAVE) and several others (Google, IBM, Microsoft etc). Commercial which can solve say an important defence standard RSA encryption in "real time": several decades perhaps (you know the saying about how it’s tough to make predictions, especially about the future....)

What are some areas of quantum information and quantum computing that no one is working in right now, but will most likely be very important in the future?

How could a field like this exist, which is both full of potential but that no one is investing in right now ? Why would people not be investing in such fields?

How do you decide which research problem is worth spending time on and which one is too intractable?

I don't like to give up on things, but a problem is intractable if you cannot solve it. For me, if I cannot solve a problem, then I’ll either (a) change techniques (b) read more and try to see if there are gaps I can fill to approach the problem again, (c) postpone it to a later time when I know I will come back to it with more experience and/or (d) resolve the issue by consulting colleagues and friends. Sometimes ideas do fail, but I try to detect the signals of failure early, learns from the failure and move on...

What, according to you, is the best scientific thought you have ever had? Basically, what is your Eureka moment? What is the story behind it?

I don't know that I've suffered a "Eureka" moment in my life...these things don't (IMHO) exist. All that exists is the accumulation of incremental hard work.
Having protested, I will share my favourite paper (co authored by me). The paper relates to connecting geometry to algebra and is titled "Generalized X states of N qubits and their symmetries". What I most enjoyed about it were the hours I spent on the topic working with my advisor, Prof. A.R.P. Rau.