Quantum Innovation: Novel Thermal Processing Increases hBN Emitter Yield Tenfold

Boron Nitride hexagon

Solid-state quantum optics advanced with the fabrication of quantum emitters in hexagonal boron nitride (hBN) by an international team. The research offers a new method for producing high-density, narrowband quantum emitters with optically programmable spins, essential for quantum sensing and information processing, led by Benjamin Whitefield and Mehran Kianinia.

Finding Reliable Quantum Interfaces

To create spin-based quantum technologies, solid-state systems where electron spins are coupled with optical transitions are needed. These interfaces allow stationary spin qubits to become “flying” photon qubits, enabling a quantum internet. Due to its unique structural properties and ability to support steady, dazzling emitters, layered Van der Waals (vdW) crystal hexagonal boron nitride (hBN) has become a prominent option.

The field has reoccurring bottlenecks. Creating isolated single photon emitters with predictable spin transitions on demand has been tricky. These faults are hard to manufacture reliably and efficiently for large-scale quantum applications.

A “Single Step” Method

The group used single-step thermal processing to manufacture a high density of narrowband quantum emitters on hBN flakes.

Narrowband quantum emitters release photons in a certain frequency range. Photons must interact and be indistinguishable for quantum networking and many quantum protocols. Thermal processing's simplicity may make quantum devices more scalable than more complicated production processes.

Record-breaking efficiency

The study's main finding is the new procedure's efficacy. More over 25% of emitters showed optical spin readouts at room temperature, according to the study.

This value stands out since it improves all previous results by an order of magnitude. In many earlier experiments, finding a functional emitter with an addressable spin was like finding a needle in a haystack. The unique approach turns the haystack into a predictable supply of quantum components. By performing these readouts at ambient temperature, quantum sensors can be widely used without expensive and huge cryogenic cooling equipment.

Understanding Spin Complexes

The analysis illuminates these faults' mechanisms. The generated spin complexes show S = 1 and S = 1/2 transitions.

Note: General quantum physics defines a doublet state as S = 1/2 and a triplet spin state as S = 1. These define the electron system's angular momentum.

Researchers explain these multiple changes using a charge transfer mechanism. In particular, charges traveling inside the hBN lattice from highly coupled to weakly coupled spin pairs cause the transitions. Understanding this complex interaction between charges and spins allows more accurate emitter control and improves our understanding of spin complexes in two-dimensional materials.

Applications in Information and Sensing

Broad implications of this work. The team's single spin-photon interactions in multilayer vdW materials enabled several high-tech applications:

Quantum Sensing: These spins inside a multilayer material can be read out at room temperature and placed near external samples. Thus, they are ideal for nanoscale temperature or magnetic field measurement. Quantum Information Processing: Photonic circuits may combine emitters due to their high density and narrowband features, making them suitable for quantum repeaters and computers.

Material Science: The study improves our understanding of spin complex-defect interactions in Van der Waals crystals.

Joint Work

Benjamin Whitefield, Helen Zhi Jie Zeng, James Liddle-Wesolowski, Islay O. Robertson, Viktor Iňdy, Kenji Watanabe, Takashi Taniguchi, Milos Toth, Jean-Philippe Tetienne, Igor Aharonovich, Mehran Kianinia, and experts in hBN crystal formation contributed to this discovery's high-quality material science.