Physicists have learned to control the quantum state of defects in diamond using sound

American scientists have built a microelectromechanical device on the basis of a diamond crystal with a nitrogen-substituted vacancies and has demonstrated the ability to control electronic spin
these defects using acoustic spin resonance.
The obtained results will help in creation of compact highly sensitive sensors with nanometer spatial resolution and low power consumption. Article published in the journal Physical Review Applied.

The diamond crystals used by physicists as
material for building devices of quantum information processing and sensitive
magnetic, electric and temperature sensors with high resolution. For these purposes, usually use crystals with defects of the lattice — nitrogen-substituted vacancies, which are abbreviated as NV-centers. They are formed by removing carbon atoms from the host lattice and binding of the vacancy with a nitrogen atom replacing one of
neighboring carbons.

For practical problems related to the management of the spin of the NV-defects, which
can be considered as a logical state of the qubits, typically use
negatively charged NV-centers, the electron spin S which is equal to
the unit (due to the presence of two unpaired electrons in this defect). According to quantum mechanics, angular momentum and associated
with it the magnetic moment of the defect is quantized and the condition of NV-centers with the lowest
energy (ground state) is
of the three spin sublevels corresponding to spin projections on some
allocated to Z axis, which are determined by the values of magnetic spin quantum
numbers, ms = -1, 0, +1.

When enabled, the external magnetic field along the axis passing through the atom
nitrogen and a carbon vacancy occurs the splitting of the spin energy
levels of the ground state of the NV-center, linearly dependent on the magnitude of the magnetic
field. If this is applied in the direction perpendicular to the weak oscillating magnetic field of microwave radiation
a certain frequency that coincides with the distance between the split
energy levels, it will lead to the absorption of a quantum of electromagnetic
field and transition the system to a state with higher energy with a change in the number
ms per unit. This phenomenon, known as electron paramagnetic
(or spin) resonance, is one of the ways of manipulating the electronic spin of the NV-centers.

The American scientists under the leadership of Greg Fuchs (Greg Fuchs) from
Cornell University has shown that for the same purpose, you can
to apply sound waves. They built a microelectromechanical device on
the basis of diamond containing NV centers, which is a bulk acoustic
a resonator with a thickness of 20 micrometers.

With the help of a piezoelectric transducer consisting of a thin layer
of zinc oxide between two electrodes, mounted with the flat side of the resonator (opposite
side had a spherical shape), within the scope of the generated standing
acoustic wave with a frequency of 2 to 3 gigahertz. The annular magnetic antenna
50 micrometers in diameter, located around the acoustic resonator
allowed to manipulate electronic transitions of the NV-centers and using traditional techniques
electronic spin resonance.

Change the state of the NV-centers that are associated with spin transitions were recorded by monitoring their photoluminescence excited by a laser with a wavelength of 532 nm using a confocal microscope.

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