As the quantum field continues to evolve, scientists keep finding better and more convenient ways to build quantum computers, and one of the most recent breakthroughs is a simplified method of selecting diamonds for use in quantum computing.
Notably, quantum computing uses diamonds with certain optically active defects as highly sensitive sensors, and researchers at Helmholtz Center for Materials and Energy (HZB) have developed a seamless method to identify these defects, according to the Science Daily report from April 15.
Specifically, these highly sensitive sensors called qubits store quantum data in the electron spin state of these color centers. However, to determine the state of each individual spin, researchers have to optically measure the photons emitted from the color center (carrying the spin).
How the breakthrough method simplifies building quantum computers
This is often experimentally complex because only single photons are emitted when spins flip, making the signature very weak. Now, the new, more elegant method solves this problem using a photo voltage to detect the individual and local spin states of these defects, which could lead to a much more compact design of quantum sensors.
As Dr. Boris Naydenov explains:
“The idea was that such defect centers not only possess a spin state, but also electrical charge.”
Hence, the HZB team modified a variant of atomic force microscopy known as Kelvin probe force microscopy (KPFM) to probe these charges. This involved a laser exciting the NV centers, generating free charge carriers captured by surface states and thus producing a measurable voltage around an NV center.
Sergei Trofimov, who conducted the measurements as part of his PhD project, said that “the photovoltage depends on the electron spin state of the NV center, and so we can actually read out the individual spin.” As he added, the new method allows capturing the spin dynamics by coherently manipulating the spin states with microwave excitation.
Per Professor Klaus Lips, head of the Spins in Energy Conversion and Quantum Information Science Department, “this would open the way to the development of really tiny and compact diamond-based devices,” because the only requirement are suitable contacts instead of complex microscopic optics and single-photon detectors.
“The newly developed readout method could also be used in other solid-state physics systems where electron spin resonance of spin defects has been observed.”
Elsewhere, a practical quantum computer could soon be a thing, as scientists at the Massachusetts Institute of Technology (MIT) have created a device that allows every processor within a quantum network to communicate directly, greatly reducing compounding error rates that have been a regular occurrence in more traditional setups.
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