Diamond Quantum Mechanics

Takayuki Iwasaki

Limin Yang, Heyi Wang, Sen Yang +1 more

Abstract Apart from being an extraordinary optical and electronic material, diamond has also found applications in quantum mechanics especially in quantum sensing with the discovery and research development of various color centers. Elastic strain engineering (ESE), as a powerful modulation method, can tune the quantum properties and improve the performance of diamond quantum sensors. In recent years, deep ESE (DESE, when >5% elastic strain, or >σ ideal/2 is achieved) has been realized in micro/nano-fabricated diamond and shows a great potential for tuning the quantum mechanical properties of diamond substantially. In this perspective, we briefly review the quantum properties of diamond and some of the corresponding sensing applications carried out with ESE, and look at how DESE could be applied for further tuning the quantum sensing properties of diamond with desired applications and what the critical challenges are.

C. Piron

Raphael Bousso A, Leonard Susskind

We argue that the many worlds of quantum mechanics and the many worlds of the multiverse are the same thing, and that the multiverse is necessary to give exact operational meaning to probabilistic predictions from quantum mechanics. Decoherence---the modern version of wave-function collapse---is subjective in that it depends on the choice of a set of unmonitored degrees of freedom, the environment. In fact decoherence is absent in the complete description of any region larger than the future light cone of a measurement event. However, if one restricts to the causal diamond---the largest region that can be causally probed---then the boundary of the diamond acts as a one-way membrane and thus provides a preferred choice of environment. We argue that the global multiverse is a representation of the many worlds (all possible decoherent causal diamond histories) in a single geometry. We propose that it must be possible in principle to verify quantum-mechanical predictions exactly. This requires not only the existence of exact observables but two additional postulates: a single observer within the Universe can access infinitely many identical experiments; and the outcome of each experiment must be completely definite. In causal diamonds with a finite surface area, holographic entropy bounds imply that no exact observables exist, and both postulates fail: experiments cannot be repeated infinitely many times; and decoherence is not completely irreversible, so outcomes are not definite. We argue that our postulates can be satisfied in hats (supersymmetric multiverse regions with vanishing cosmological constant). We propose a complementarity principle that relates the approximate observables associated with finite causal diamonds to exact observables in the hat.

Rainer Dick

M. W. Doherty, Carlos A. Meriles, Audrius Alkauskas +3 more

Diamond is a proven solid-state platform for spin-based quantum technology.The nitrogen-vacancy center in diamond has been used to realize small-scale quantum information processing and quantum sensing under ambient conditions.A major barrier in the development of large-scale quantum information processing in diamond is the connection of nitrogen-vacancy spin registers by a quantum bus at room temperature.Given that diamond is expected to be an ideal spin transport material, the coherent transport of spin directly between the spin registers offers a potential solution.Yet, there has been no demonstration of spin transport in diamond due to difficulties in achieving spin injection and detection via conventional methods.Here, we exploit detailed knowledge of the paramagnetic defects in diamond to identify novel mechanisms to photoionize, transport, and capture spin-polarized electrons in diamond at room temperature.Having identified these mechanisms, we explore how they may be combined to realize an on-chip spin quantum bus.