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A Dissipatively Stabilized Mott Insulator of Photons (1807.11342v2)

Published 30 Jul 2018 in cond-mat.quant-gas and quant-ph

Abstract: Superconducting circuits are a competitive platform for quantum computation because they offer controllability, long coherence times and strong interactions - properties that are essential for the study of quantum materials comprising microwave photons. However, intrinsic photon losses in these circuits hinder the realization of quantum many-body phases. Here we use superconducting circuits to explore strongly correlated quantum matter by building a Bose-Hubbard lattice for photons in the strongly interacting regime. We develop a versatile method for dissipative preparation of incompressible many-body phases through reservoir engineering and apply it to our system to stabilize a Mott insulator of photons against losses. Site- and time-resolved readout of the lattice allows us to investigate the microscopic details of the thermalization process through the dynamics of defect propagation and removal in the Mott phase. Our experiments demonstrate the power of superconducting circuits for studying strongly correlated matter in both coherent and engineered dissipative settings. In conjunction with recently demonstrated superconducting microwave Chern insulators, we expect that our approach will enable the exploration of topologically ordered phases of matter.

Citations (290)

Summary

  • The paper demonstrates that engineered reservoir dissipation in a superconducting photonic lattice can stabilize a Mott insulating phase with high fidelity.
  • Using a one-dimensional Bose-Hubbard lattice of transmon qubits, the experiment effectively mitigates photon loss while enabling precise site-resolved monitoring.
  • Numerical simulations and the observation of light-cone-like photon dynamics confirm the method's robustness, paving the way for exploring complex quantum states.

Summary of "A Dissipatively Stabilized Mott Insulator of Photons"

The paper explores the stabilization of Mott insulators within a photonic Bose-Hubbard lattice realized through superconducting circuits. This work provides crucial insights into designing synthetic quantum materials composed of microwave photons by leveraging the unique properties of superconducting circuits: high coherence times, controllability, and strong interactions. The intrinsic photon losses that generally hinder the realization of quantum many-body phases in such setups are mitigated using reservoir engineering, allowing the dissipative preparation of incompressible many-body states.

Overview of the Research

The authors have constructed a one-dimensional Bose-Hubbard lattice employing transmon qubits to investigate the interactions of photons within the strongly correlated regime. The lattice demonstrates high coherence and controllability, with site-resolved readouts enabling precise tracking of photon dynamics. The problem of photon loss, which typically leads to decay into the vacuum state, is addressed by introducing a method for dissipative stabilization. This method involves using a reservoir to autonomously stabilize specific quantum states, effectively using dissipation as a resource for quantum stabilization.

The method specifically targets a Mott insulator, a state characterized by its incompressibility and energy gap. Effective stabilization of the Mott phase was achieved by coupling the lattice to an engineered reservoir that balances photon injection and dissipation, preventing further particles from being added beyond a target state energy differentiated by a compressibility gap. The stabilization techniques employed are akin to optical pumping strategies in atomic physics, with the added advantage of being applicable in creating synthetic quantum phases of matter.

Experimental Setup and Methodology

The experiment utilized an array of transmon qubits as lattice sites, with tunable frequencies and on-site interactions characterized by anharmonicity. The effort to realize this complex setup involved addressing challenges of photon loss through an autonomous stabilizer. In particular, two different stabilization schemes were tested, adapting approaches common in atomic physics to novel photonic systems:

  1. Single Transmon Scheme: Utilizes on-site interactions to stabilize a single photon's state by facilitating a dissipative transition between the n=2n=2 and n=1n=1 photon states.
  2. Two Transmon Scheme: Involves a more complex interaction between two transmons and a reservoir, facilitating an energy-specific dissipation process that leads to enhanced stabilization performance.

Both methods showed that carefully engineered dissipation could overcome challenges posed by losses, achieving efficient stabilization of quantum phases like the Mott insulator.

Results and Implications

The paper succeeded in demonstrating a Mott insulating phase stabilized by reservoir engineering, a pivotal step towards exploring more complex quantum states in photonic systems. Key findings include:

  • The successful demonstration of dissipative stabilization of Mott insulators with high fidelity.
  • Observation of light-cone-like dynamics in photon filling, indicating ballistic transport in the lattice.
  • The ability to refill defects within the stabilized phase, showing potential for studying defect dynamics in strongly correlated states.
  • Numerical simulations corroborated experimental results, highlighting the method's robustness against thermal reservoir effects.

Future Directions

This work paves the way for further exploration of topologically ordered states and complex quantum phases in photonic systems. Future studies might focus on:

  • Extending these techniques to larger and more complex photon lattices.
  • Investigating defect dynamics within other strongly correlated or topologically ordered phases.
  • Exploring thermalization and prethermalization behaviors within dissipatively prepared states, potentially offering new insights into the nature of quantum phases beyond equilibrium.

In conclusion, this research expands the toolkit available for exploring quantum many-body physics with photons, demonstrating that engineered dissipation can be a powerful tool for navigating the challenges of photon loss in superconducting circuits.