Ultraviolet laser pulses engineer diamond defects selectively, leaving quantum qubits intact
When we think about a diamond, we often think about a material whose value comes from its perfection. In my research, however, I am interested in something almost opposite: the tiny imperfections inside diamonds. These atomic-scale defects can give diamonds new optical and electronic properties, and some of them can serve as quantum systems. The challenge is learning how to control these defects…
Diamonds are often admired for their flawless perfection. However, the tiny imperfections within them can imbue these gemstones with novel optical and electronic properties, making them suitable for quantum systems. A major challenge lies in controlling these defects without disturbing the others, particularly in the realm of quantum technologies.
One example of such a defect is the nitrogen-vacancy (NV) center, which consists of a nitrogen atom and a vacancy in the diamond lattice. NV centers can function as quantum bits, or qubits, and serve as highly sensitive sensors of magnetic and electric fields. To achieve precise control over individual defect populations, researchers explored the potential of ultraviolet laser pulses for selective modification of diamond defects, leaving quantum qubits unaffected.
In this study, published in Diamond and Related Materials, the researchers employed a single-crystal chemical vapor deposition (CVD) diamond and irradiated localized regions with ultraviolet laser pulses of 266 nanometers, only a few nanoseconds in duration. The aim was to determine if localized optical excitation could modify specific defects within the lattice without affecting others.
Before irradiation, the pristine diamond was characterized using various spectroscopic techniques to establish the initial optical defect landscape, including the presence of substitutional nitrogen. Upon laser irradiation, a new optical emission near 563 nanometers appeared in the laser-exposed regions, alongside another feature near 579 nanometers.
These emissions are associated with defect configurations involving carbon self-interstitials. Importantly, the existing NV centers within the diamond remained largely unchanged after the laser treatment, indicating that the laser could selectively produce a measurable change in one defect population without significantly affecting another.
This selective manipulation of defect populations while preserving the preexisting quantum-relevant defect population is significant for the development of quantum technologies based on diamond. The researchers suggest that sub-bandgap ultraviolet photons interact with defect-associated electronic states, causing localized electronic excitation and subsequent energy transfer to the surrounding lattice, potentially leading to the rearrangement of carbon atoms near existing defect sites.
However, establishing the complete microscopic pathway remains an open question, necessitating further experiments. The study demonstrates the feasibility of using nanosecond ultraviolet laser irradiation to selectively modify the optical defect structure of single-crystal CVD diamond while preserving the background NV-center population, potentially offering a valuable tool in the broader toolbox for quantum technologies based on diamond.
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