Research
Quantum Error Correction
One of the central challenges in building a quantum computer is that the qubits do not maintain their quantum nature
for a very long time. This phenomena is called decoherence and happens primarily due to environmental noise. However,
it is possible to use multiple imperfect qubits to build a near-perfect qubit using a process called quantum error
correction. This involves encoding the single qubit state among multiple physical qubits, making the right kind of
measurements to detect any errors and then use feedback to correct those errors. We are investigating techniques to
implement quantum error correction using weak continuous measurements and feedback.
Quantum Simulations
The computational resources required to simulate quantum mechanics on a classical computer grows exponentially with
the size of the simulated system. Feynman had originally suggested that one should use
quantum systems to simulate quantum mechanics. The basic idea is to have a well
characterized and controllable quantum system to mimic the behaviour of other systems of
interest. Our lab is interested in studying collective behaviour in superconducting qubits
and developing the necessary architecture for performing quantum simulations.
Novel qubit designs
We are working on novel qubit designs where a single superconducting circuit can be used to implement a
coupled multi-qubit system. We are exploring such multi-qubit systems for quantum error correction and quantum simulations.
Quantum limited parametric amplifiers
Parametric amplifiers have become an essential component of high fidelity quantum measurement setups. We are working
on developing new amplifier designs which have enhanced bandwidth (
See paper here) and dynamic range to enable multiplexed
multi-qubit measurements. Such amplifiers will also enable new experiments in microwave quantum optics.
Weak quantum measurements
We are exploring weak quantum measurements in superconducting circuit QED architecture for applications in
quantum error correction, quantum feedback and quantum metrology.
Nanomechanical systems in the quantum regime
Recent advances in nano-fabrication techniques have enabled the fabrication of nano-mechanical
oscillators capable of displaying quantum phenomena. We are working on combining such nano-mechanical oscillators
with superconducting circuits to explore new regimes in quantum measurement.
Useful links
A review article on superconducting quantum bits : Link
A more recent review article on superconducting quantum bits : Link
Vijay's talk at Dartmouth College in 2012: Abstract
||Video
A classic reference for Quantum Computing and Quantum Information:
Link
Useful Theses
One of the first thesis on superconducting qubits: Cottet's Thesis
Vijay's thesis on the Josephson Bifurcation Amplifier: Vijay's thesis
David Schuster's thesis on circuit quantum electrodynamics (cQED) architecture: Schuster's Thesis