IRG 3 Engineering Quantum Materials and Interactions

There are significant advantages to developing quantum systems in which strong coupling, high fidelity control, and very long quantum coherence times are all achieved simultaneously. Quantum sensing has revolutionized metrology, perhaps most strikingly in the form of atomic clock measurements, Time has now been measured to a precision of 10-18 by assembling individual atomic clocks in an optical lattice, making it arguably the most precise measurement in human history. Furthermore, using ultracold atomic gases, it is now possible to perform simulations of quantum many-body problems that are intractable with modern classical computers. While such measurements have been performed using atoms as the paradigms of quantum mechanics, it has recently become possible to realize solid-state systems with atom-like coherence. Surprisingly, quantum spin defects in a semiconductor, the centers that can give gemstones their color, may be manipulated as though they are isolated atoms frozen into solid form. These “defects,” often living in a disordered solid-state environment, have spin coherence times that rival atoms in vacuum, even at room temperature. This IRG seeks both to push the bounds of what can be done with atomic systems, and adapt their experimental techniques traditionally used for studying ultracold atoms to the promising but less mature area of quantum spin defects. We intend to understand the physics underlying the individual quantum systems, to scale these systems upwards in a quantum coherent manner, and ultimately to explore emergent properties of such large-scale quantum systems. Applications of this work range from building quantum sensors to realizing new classes of material such as topologically protected systems.

This IRG seeks to focus on the critical issues of quantum control and quantum coherence, issues that face distinct challenges in individual, few-body and multi-mode quantum systems, but with significant overlap across all three size scales. The IRG builds on our collective combined expertise in studying macroscopic coherence in both ultracold atom and solid-state materials. The central aim of this IRG is to develop a common platform and theoretical understanding that will allow systematic development of high performance quantum systems. The group members will collaborate to engineer the coherence and interactions of solid-state spins with one another and with bound photons and phonons; the team will engage in a parallel effort to develop analogous atomic systems. We will focus specifically on spin-active color center defects in aluminum nitride (AlN), silicon carbide (SiC) and diamond, with a parallel effort on understanding comparable model systems based on cold atom gases, in which direct control of the interaction Hamiltonian is possible. We will explore system sizes ranging from single spins to large-scale quantum meta-materials by combining individual quantum states that can be operated in few-body or in many-body collective modes without destroying the performance of the individual components.

We have divided the effort of this IRG into three Focus Areas, as the challenges and techniques to understand and improve the coherence of both condensed matter and atom-based quantum systems change with the size scale of the system being developed. In Focus Area 1, “Physics leading to quantum defects”, we concentrate on developing theoretical and experimental understanding of individual solid state spin defects that incorporate additional degrees of control and functionality, for which the primary decoherence mechanisms and spin-lattice and spin-spin interactions are still not understood. Developing a better understanding of the fundamental physics of these quantum elements will lead to significantly improved performance and technological applications at the level of individual spins. In Focus Area 2, “Quantum control of few body systems”, we explore new modalities and model systems for achieving quantum control of hybrid condensed matter and atomic spins, developing new approaches to fully quantum photon-spin and phonon-spin control, and in atomic systems exploring coupled Cs spins in a Li matrix, where small spin numbers can be generated and made to interact with a controlled Hamiltonian. The condensed matter effort in Focus Area 2 will build on the understanding of individual quantum defects developed in parallel in Focus Area 1. Finally, in Focus Area 3, “Engineered quantum materials”, we will construct and investigate collective systems in which we seek to demonstrate emergent behavior. Focus Area 3 will employ the interaction modalities studied in Focus Area 2, and extend them to realize strongly coupled microwave photon toplogical modes in the solid-state, and in cold atom gases strongly coupled Rydberg-polariton collective modes, in which Rydberg electromagnetically induced transparency is used to generate the collective modes.


The goal of this IRG is to create and explore new classes of quantum materials which exhibit engineered coherence from its “atomic” constituents to its macroscale properties. Emulating the precise quantum control of atomic systems in solid state materials allow us to address critical theoretical questions in materials science, including the origins and consequences of topological states of matter, near and far from equilibrium transport, and single and many-particle coherent interactions. Tackling these questions is greatly enhanced through the coordinated study of related solid-state and AMO systems by a wide range of interrogation methods, made possible by the unique interdisciplinary institutes and diverse expertise available at Chicago. The proposed research will directly advance applications in quantum sensing, materials for quantum information as well as the next generation of characterization tools for traditional materials.

Proposal for a synthetic gauge potential in an optical lattice a) depending on shaken lattice in 2D (b) combinations of the 4 ground states (c) and stabilization. This was also realized experimentally
Spatial mapping mechanical spin driving in a Gaussian SAW resonator.
Schematic of cavity layout. White circles denote cavities allowing photon phases to remain unshifted, while arrows denote cavities that shift photon phases. B) Photo of the lattice. c) Side profile.
(left) Transmission spectrum b/w two bulk (purple) and edge (orange) sites. (right) Projected band structure of both the bulk (blue/white plot) and edge (red points) of system, compared with theory.
Single photon-phonon coherent transfer sequence and qubit population versus detuning ∆ and interaction time τ. The qubit frequency is set to the SAW resonance and the coupling is turned on for ~37 ns
Time evolution of Bose-Einstein condensates subjected to a periodic driving force. The condensate is ejected from the trap in the form of matter wave jets. Theory (top) experiment (bottom).