Welcome to the Quantum Devices Group! We develop quantum hardware for applications in quantum communication, computation, and sensing. We build novel quantum devices based on superconducting qubits and atom-like defects in engineered phononic and photonic nanodevices. By controlling interactions between these different quantum systems with unique strengths, we are developing new device architectures for future quantum technologies and gaining new insights into quantum dynamics and coherence in nanoscale systems. 

Current research directions: 

Quantum nonlinear silicon photonics

Silicon is the ideal material platform for building electronic and photonic circuits at scale. Linear or weakly nonlinear silicon photonic circuits are widely pursued to realize all-optical quantum processors. However, the lack of deterministic two-qubit gates and single photon sources in these architectures result in very large resource overheads that pose a major challenge to scaling.

We are developing quantum nonlinear silicon photonics that will enable deterministic interactions between single photons and spin qubits. To achieve this, we are developing spin-photon interfaces in integrated silicon photonics. The questions we study include: 

  • Color center qubits in silicon: How do we design an “ideal” atom-like, color center qubit in silicon? What are the desired defect symmetries, spin, electronic and optical properties? This is our defect genome project
  • Device integration: Integration of artificial atoms into silicon photonics to realize deterministic spin-photon, photon-photon, and long range spin-spin interactions at high bandwidths. 
  • Quantum repeater nodes: Developing a practical quantum repeater node based on silicon color centers for the UC Berkeley – LBL Quantum Network Testbed. 

Our long-term vision is to develop the missing ingredients that would enable practical quantum computers and communication nodes at silicon foundries. 


Ultracoherent superconducting electromechanical qubits

Superconducting quantum circuits are currently the leading solid-state quantum computing platform. Despite their remarkable progress, we are yet to fully understand and control dominant dissipation mechanisms that lead to high physical qubit error rates. 

In the past few years, a new field of quantum phononics has emerged. Recent advances have shown that single phonons can be coherently controlled and can make good qubits! We recently found that nanomechanical resonators can have ultra long lifetimes, and can be used to transduce quantum states from superconducting qubits to optical photons.

In this effort, we are building on recent advances in quantum phononics to advance superconducting quantum processors. We are modeling and engineering how qubits interact with their phonon bath to improve qubit coherence. To achieve this, we are studying microscopic dissipation mechanisms, and developing novel electromechanical qubit architectures with highly protected electrical and mechanical quantum degrees of freedom.

Our near term goals include: modelling materials origins of qubit-phonon interactions, designing phonon-protected superconducting qubits, and engineering ultracoherent nanomechanical resonators for bosonic quantum information processing.