Research Interests

I am interested in wide range of topics related to quantum information theory. It all started with my PhD thesis on “Quantum state discrimination with Gaussian states" with Seth Lloyd at MIT in which I worked on a class of continuous variable states, the Gaussian states, for quantum communication protocols. Following my graduation in 2010, I started working at the Data Storage Institute (A*STAR, Singapore) with the experimental group of Leonid Krivitsky on more industry-applied problems focusing on quantum optical applications of quantum information theory using photon-pairs produced by non-linear photonic crystals and semi-conductor photon-number-resolving detectors. Since 2014, I have been working in the group of Joseph Fitzsimons where I switched gears to look into verifying quantum computations, and constructing new quantum cryptographic protocols.

Here are the details of my active area of research:

(1) Quantum homomorphic encryption

In the world of classical cryptography, homomorphic encryption is a hot topic of research since 2009 when Gentry constructed a fully homomorphic encryption scheme that is believed to be computationally secure. Homomorphic encryption is a cryptographic primitive that allows for the processing of ciphertext without giving away the key that is used for encryption. I have been using quantum mechanical systems to implement quantum homomorphic encryption for data represented on quantum states. The advantages of such quantum schemes is two-fold. First, they have information theoretic security which is not premised on any hardness assumptions. Second, the classes of quantum computations that can be performed may include stuff that is hard to simulate on classical computers.

(2) Quantum optics: Photon-counting

Many technological applications of quantum optics require the use of photon-number-resolving detectors (PNRDs) which are named for their ability to resolve between N and N+1 photons, for N>1. However, these PNRDs suffer from noise and losses.  I look at how these artifacts influence measurement of quantum correlations, such as g(2) and higher-order correlations, and the noise reduction factor. 


(3) Quantum interferometry

Photons scatter through an interferometry just like fermions would in potential fields. Although they obey the bosonic commutation relationship and do not couple to each other, many interesting quantum mechanical effects happen in these interferometer. One such effect is the Hong-Ou-Mandel or photon-bunching in which two single photons impinging on a beamsplitter tends to emerge together and the coincidence (one photon in each outcome) is extinguished. I am interested in the generalization of these types of effects and also in the engineering of these states for use in demonstrating them.


(4) Quantum measurements and decoding

Optical communication using quantum states through quantum channels is an interesting extension of the classical Gaussian channels. To be able to harness the ``quantum advantage" afforded by preparing and using states and channels, we have to construct explicit receivers which are immediately implementable using available known methods from classical coding, non-linear optics and sequential waveform nulling.