What are Quantum Materials? What is the future of Quantum Materials research?
Michael J. Manfra, Purdue University
William D. Oliver, Lincoln Laboratory, Massachusetts Institute of Technology
David Pappas, National Institute of Standards and Technology
Maya Cassidy, Microsoft/ University of Sidney
Malcolm Carroll, Sandia National Laboratories
Josh Mutus, Google Quantum Hardware
Chih Wei Lai, US Army Research Laboratory
Christopher J.K. Richardson, University of Maryland
Written by Xun Gong
What are Quantum Materials?
Quantum materials seems to be an exotic buzz word in physics with no community consensus. To define quantum materials, there needs to be, first, a clarification of terms. It can be said that quantum materials are any materials that are involved in the construction of quantum-based information systems. This can include superconductors, diffusion barriers, and insulators, including new forms of nonclassical materials. This should be differentiated from quantum information, which can be defined as a subset of quantum materials from which information can be present on the quantum level, observing certain criteria (detailed below). One potential illustrating analogy is that quantum materials is to quantum information materials as semiconductors is to semiconductors for resistor applications.
A well-known set of rules called the DiVincenzo criteria describes requirements for quantum information. A material can sufficiently carry quantum information if it has at minimum the properties of (1) having a 2 level system with (2) long coherence times. It must have (3) a universal set of qubit gates (a qubit being a unit of quantum information), be (4) able to initialize in a known state, and finally (5) read out what happened. For example, organic molecules have short coherence times, which make them difficult for this application.
When the panelists were asked why quantum information systems require super low temperatures, they responded:
- There are high levels of quasiparticles at high temperatures, which are unknown disturbances that add significant noise to the system.
- The state transition frequency should be larger than temperature of the environment, this way ground states can be initialized without noise.
- Overall, there needs to be an improved understanding of noise contributions in the system, as qubits are practically the most sensitive sensors for parasitic sources of noise. Much of these noise contributions is due to lack of understanding of materials surfaces and defects, as well as how different materials interface and interact. These new materials interfaces and properties should be of interest to materials researchers and physicists alike.
What are the tools for analysis of quantum materials?
Currently the dilemma with analytical tools is that either today’s tools cannot detect the properties we are not looking for or we are unable to extract the appropriate data (in reference to TEM/XPS). Room exists for new techniques or novel implementation of current methods. There is also a need for the development of new computational tools to study materials interfaces. Currently there is doubt in the physics community about the accuracy of materials simulation methods. This might be due to the fundamental assumptions of the simulation packages in addition to their inefficiencies in simulating a larger set of materials with a wide array of potential defects. This simulation is of a difficult scale as it is not so small so that they are trivial to run, but also not large to the extent of the bulk.
To the question: What can the fields do jointly for the future? the panelists say:
- Provide mechanisms for joint grants between the physics and materials researchers.
- The quantum community needs to prove to funding agencies that quantum computers have a specific niche application that classical computation cannot achieve.
- Materials researchers need a list of properties to look for in terms of quantum-related applications.
- A new set of training might be needed to prepare students with fundamentals in both fields (e.g., quantum engineering).
- Lastly, it may not be a good idea to draw rigid boundaries for the area of quantum materials, because drawing boundaries might limit creativity and become a barrier to entry.