EAGER: Generating Motional Quantum States of an Optically Trapped Diamond Nanocrystal Containing Nitrogen Vacancy Centers

Montana State University, Bozeman MT

Investigators

Abstract

The motions of objects in everyday life appear to follow simple rules (Newton's laws). For example, a hockey puck gliding across ice tends to keep moving in a straight line at constant speed unless a force acts on it. It is implicit in Newton's laws that you can always measure everything about the puck's motion, such as its position and its speed, without affecting the motion. It seems that the same should be true of any object, whether it is huge like the planet earth or tiny like an atom. However, this is not how nature works; very small objects, such as an atom or an electron, seem to obey a different set of rules, called quantum mechanics. Quantum mechanics predicts that strange things can happen, for example, an atom can have properties of being in two places at the same time, until its position is actually measured. As strange as those rules are, they make the electronics in computers and cell phones work, so we know they are accurate. Why don't hockey pucks have this strange quantum behavior? Interaction with other objects tends to hide the effects of quantum mechanics for objects much larger than atoms. The research team supported by this project will levitate a tiny diamond crystal in a chamber with almost no air remaining to minimize its interaction with other objects and stretch the size limits over which quantum mechanics does apply. The results of these experiments will improve our understanding of quantum mechanics, which is the foundation on which almost all our modern technology is based. This program ultimately seeks to produce "cat states" in a mechanical system, where an object is in a quantum superposition of two different positions. This is a challenge which has puzzled physicists since the famous thought experiments of Schrodinger, 80 years ago. Researchers supported by this program will demonstrate that a trapped diamond nanocrystal containing nitrogen-vacancy (NV) defect centers is a nearly ideal platform for creating such motional quantum states. In particular, they will work towards demonstrating four critical capabilities of this system. First, the diamond nanocrystal must be trapped in vacuum with an ultra-high quality factor (Q). Second, it must be possible to manipulate and read out the spin state of the NV centers. Third, the NV center spin states must couple to the state of the mechanical motion. Last, the mechanical motion must be cooled to near the ground state to initialize the system to a known configuration. The experiments begin by loading a diamond nanocrystal into the trap. Next, the spin state of NV centers in the trapped nanodiamond will be read optically and manipulated with a microwave drive. Finally, the mechanical motion is coupled to the NV center spins through externally-imposed magnetic field gradients. The combination of the ultra high Q of the mechanical motion and quantum control of the NV centers makes trapped, NV-containing nanodiamonds a unique system for generating motional quantum states. The development of this system could be of great value in exploring the fundamental limits of quantum mechanics and the properties of novel motional quantum states. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.