About us

                Welcome to the page of Tim Byrnes at NYU Shanghai -- New York University's campus in Shanghai. We do research into theoretical quantum information, atom optics, and condensed matter physics.  Find out more about who is involved in this research, and opportunities to work with us through internship programs.  Information on getting to NYU can be found on the contacts page.

What we do


Atomic Bose-Einstein condensates are the coldest things known in the universe, even colder than deep space.  At such low temperatures strange quantum effects such as entanglement become strong enough that it is important.  Here we describe a little about our research of understanding this unique state of matter and application towards  quantum information.

Accelerated optimization using Bose-Einstein condensates

When a Bose-Einstein condensates (BECs) forms, all the bosons undergo a phase transition such that they enter the lowest energy state of the system.  Meanwhile, many computationally difficult problems can be reformulated into an optimization problem.  The idea here is that we use the power of BECs to solve a given optimization problem. Unlike standard quantum computing where superposition is the resource, here we are using indistinguishability to solve the problem. Find out more

BEC-BCS crossover of exciton-polaritons

An exciton is an composite particle made of an electron and a hole, which are both fermions.  Since two fermions make a boson, an exciton is a bosonic particle which can potentially undergo Bose-Einstein condensation.  At high density the underlying fermionic components of the excitons start to play a role, and it is known that the state is more like a BCS-state, familiar from superconductivity.  But what happens for exciton-polaritons? Find out more

Exciton-polariton condensates and new quantum technologies

Exciton-polaritons are particles that live inside semiconductor microcavity structures, when they are illuminated by laser light.  Recently these particles have been observed to undergo Bose-Einstein condensation (BEC).  Unlike atomic systems that require nanokelvin temperatures in order to under BEC, exciton-polaritons typically only require about 10K, or even higher depending on the materials chosen.  This opens the question: what kind of new technologies will these discoveries bring? We investigate this along several lines of thought, from quantum simulation to light emitting devices. Find out more

Novel light sources using exciton-polaritons

  Lasers have found many uses in society, taking advantage of the useful properties of coherent light.  In a normal laser the photons do not interact, which leads to a Wigner function that is positive everywhere.  Here we develop a new type of laser based on exciton-polariton condensates that produce light with a negative Wigner function completely deterministically and continuously.  Find out more

Quantum information using Bose-Einstein condensates

Today groups across the world are experimenting with various technologies in the pursuit of novel quantum information processing devices.  Some of the more famous examples are ion traps, quantum dots, superconducting qubits, cold atoms in optical lattices, N-V centres in diamond, and photons.  Here we are interested in using Bose-Einstein condensates for quantum information, which are interesting because they exhibit quantum phenomena on a macroscopic scale! Find out more



Full name: Jiaqi Xi

Position: Undergraduate Research Assistant

Nationality: Chinese

Career: 2015-2019 B.Sc in Honors Mathematics at NYU Shanghai



Comments are closed.