Physicists have learned to extract information from a quantum mechanical system without disturbing the quantum state

Physicists from ETH Zurich have linked a mechanical resonator with a superconducting quantum resonator

The technology, developed by the scientists and described in an article in the journal Nature Physics, allowsMeasure the quantum properties of a mechanical cavity system without disturbing the quantum state.

Scientists use a plate as a resonatorhigh-quality sapphire with a thickness of just under 0.5 mm. At its top is a thin piezoelectric transducer that can excite acoustic waves that are reflected from below and thus propagate through a well-defined volume within the slab. The researchers note that these excitations represent the collective movement of a large number of atoms, which are quantized (in photons) and can be subjected to quantum operations.

Electromagnetic fields associated withsuperconducting circuit, ensure the connection of the qubit with the piezoelectric transducer of the acoustic resonator and thus with its mechanical quantum states.

Image: von Lüpke et al., Nature Physics

The researchers note that in their experiments, nothere is a direct exchange of energy between the superconducting qubit and the acoustic resonator during the measurement. Instead, the properties of the qubit depend on the number of phonons in the acoustic resonator. This approach makes it possible to study the mechanical quantum state in a "non-contact" way.

In their study, the physicists were able to extract the distribution of the number of phonons in their acoustic resonator after excitation by different amplitudes.Moreover, they demonstrated a way to determine, in a single measurement, whether the number of phonons in a resonator is odd or even—the so-called parity measurement—without any further information about the distribution of the phonons. 

Scientists note that obtaining just such a veryspecific information, rather than any other, is crucial in a number of quantum technological applications. For example, a change in parity (going from an odd number to an even number or vice versa) can signal that an error has affected the quantum state.

The researchers plan to continue working ontechnology to enable full control of a quantum mechanical system, such as error correction, while still maintaining a quantum state.

Read more

American satellite "saw" an unusual message from Earth

Published video from the rocket, which was launched from an experimental accelerator

The monster at the center of our Galaxy: look at the photo of a black hole in the Milky Way