Chen Wang Lab

Welcome to the Chen Wang Lab in the department of physics at University of Massachusetts-Amherst!

We work in the field of superconducting circuit devices for quantum information processing, with a focus on improving the performance of superconducting quantum bits (qubits) on both the physical and the (error-corrected) logical level.  We are part of the device thrust of the Co-design Center for Quantum Advantage (C2QA), a Department of Energy QIS center under the US National Quantum Initiative (and we are currently looking for a postdoc to work under the C2QA center).

Our superconducting qubit is made of a micro-fabricated aluminum thin-film structure on a sapphire substrate, containing one or more Josephson tunnel junctions.  When the device is cooled down to very close to absolute zero temperature (~10 mK, much lower than the T_c of aluminum) in our dilution refrigerators, it can be understood as an “artificial atom”: The cloud of electrons (forming a Cooper-pair condensate) in an isolated aluminum island collectively orbit around the lattice without friction, just like electrons orbit around the nucleus.  The resultant discrete orbitals represent the ground, first excited, second excited states, etc.  We use racks of electronics, including arbitrary waveform generators, RF synthesizers, I-Q mixers to generate programmable microwave pulse sequences to manipulate and measure the quantum states of these qubits, including superposition and entangled states.  Operations of superconducting qubits are conceptually very much like in atomic physics, where lasers and real atoms are replaced with microwaves and artificial atoms.

Leveraging the ability to freely design the Hamiltonian parameters of our quantum systems and the ability to engineer time-dependent microwave control fields, we have created some fascinating quantum states and phenomena the natural world has never seen:

— (An analogy of) A Schrodinger’s cat, dead and alive, simultaneously in two boxes.  This modern fusion of the Schrodinger’s infamous paradox and Einstein’s “spooky action at a distance”, has been reported in Science, various news media (see e.g. Science Daily, Washington Post, Live Science), and featured as one of the top-10 Physics World 2016 breakthroughs of year.

— An exotic environment that runs a quantum error correction code in its sleep.  For two decades experimental quantum error correction grew hand-in-hand with delicate quantum measurements, complex active electronics and fast digital feedback.  Our recent breakthrough published in Nature 2021 (also see news at e.g. Phys.org, Science Daily) marks a dream coming true — the dominant physical errors in a logical qubit are automatically corrected by only a constant supply of energy and dissipation in the background.

More about our research can be found on the Research page.