Light directed spatial omics

This is the research area I am working on as a postdoctoral research fellow. Cells have molecules called RNA and one of their crucial functions is to carry information from genes stored in DNA to make proteins. The set of all RNA in a cell is called its transcriptome and typically contains several thousand RNAs. Information of the transcriptome can give us a variety of information including what type of cell it is, if the cell is functioning properly, or what genes are activated under stimuli. Combined with information of where that cell is positioned in relation to others in a tissue can now start to help us understand how the tissue functions from a ground-up approach. There are two classes of methods that perform such spatial omics measurements: imaging-based, which has high resolution but is selective in the transcriptome, and sequencing-based, which has lower resolution but can measure the transcriptome unbiased. I am developing a method to combine the two approaches to use light and sequencing to bridge the gap between them to have high-resolution and unbiased measurements. The hope is that high-quality characterization of molecules in tissues can help us understand them better!

Multiplexed optical barcoding and sequencing for spatial omics

A Venkatramani*, D Ciftci*, L Cohen, C Li, K Pham, X Zhuang

BioRxiv (2024)

Nonlinear quantum optics

This is primarily work that I did during my graduate studies wherein we created strong interactions between single photons. Photons, which are single quanta of light do not interact strongly with one another. Having single photons interacting with each other such as one photon acting as a switch of other photons, inducing phase shifts on another photon, or having a photon transistor opens the possibility of having all optical devices which can be faster and more power efficient. In addition to optical devices, photons are great candidates for long distance communication. Most modern long distance communication is transmitted via fiber optics since light has a high frequency and bandwidth. This idea can be extended to the quantum realm by using strong photon interactions to map qubit states onto photons and transmit it on a network. Our works have demonstrated tunability and robustness in interactions that allow extensive control of strongly interacting photons. We have been able to coherently create exotic states of light including molecules of photons and repulsive photons with indications of a crystal structure.

Fast preparation and detection of a Rydberg Qubit using atomic ensembles

A Venkatramani*, W Xu*, S Cantu*, T Sumarac, V Klusener, M Lukin, V Vuletic

Physical Review Letters (2021)

Repulsive photons in a quantum nonlinear medium

A Venkatramani*, S Cantu*, W Xu, L Zhou, B Jelenkovic, M Lukin, V Vuletic

Nature Physics (2020)

(Physicsworld)

Observation of three-photon bound states in a quantum nonlinear medium

Q-Y Liang, A Venkatramani, S Cantu, T Nicholson, M Gullans, A Gorshkov, J Thompson, C Chin, M Lukin, and V Vuletic

Science 6377,783-786 (2018)

(MIT news, Smithsonian, some fun, and more fun)

Symmetry-protected collisions between strongly interacting photons

J Thompson, T Nicholson, Q-Y Liang, S Cantu, A Venkatramani, S Choi, I Fedorov, D Viscor, T Pohl, M Lukin, V Vuletic

Nature 542, 206–209 (2017)

Quantum information with superconducting circuits

This is work that I did during my undergraduate years in Berkeley and an internship at the experimental quantum computing group at IBM. This was my introduction into the world of quantum computing. Light can be described as a distribution over two quadrature variables wherein we cannot know both values precisely from quantum uncertainty. It is however possible to reduce the uncertainty of one of the quadratures by trading off an increased uncertainty in the other quadrature. This process is called squeezing and can be beneficial for measuring states of quantum bits. My undergraduate thesis was creating and studying these squeezed states of light at microwave frequencies.

Effect of higher-order nonlinearities on amplification and squeezing in Josephson parametric amplifiers

S Boutin, D Toyli, A Venkatramani, A Eddins, I Siddiqi, A Blais

Phys. Rev. Applied 8, 054030 (2017)