Starting point / motivation
Recent years have seen a leap in the technological readiness of a variety of quantum technologies, and there has been increasing interest in quantum technology for applications in space. Examples are quantum key distribution over global distances, long-distance tests of quantum entanglement, and possibilities to boost the sensitivity of high-precision measurements in space. Moreover, space offers a unique environment for tests of the foundations of quantum physics.
A promising quantum technology for high-sensitivity sensing and for fundamental tests is quantum optomechanics, where massive mechanical resonators are operated in the quantum regime. One of the central challenges in such experiments is to isolate the quantum systems from detrimental interactions with the environment (decoherence).
To this end, it was suggested to use optically trapped dielectric spheres instead of mechanically clamped oscillators. This approach is at the heart of the MAQRO proposal to use quantum optomechanics and high-mass matter-wave interferometry to test the foundations of quantum physics. Even in this case, the quantum system can decohere in multiple ways.
A key limiting factor are collisions with gas/plasma particles. For that reason, quantum experiments like MAQRO would require extremely high vacuum (XHV) conditions – ideally <=1e-15mbar. Apart from the challenge of reaching XHV in space, it is no trivial task to detect such vacuum levels.
Contents and goals
The present proposal intends to harness the extreme sensitivity of quantum systems to gas collisions in order to realize an XHV-capable sensor using an optically trapped sphere. Experiments have shown an increasing level of control in such systems, and very recently, the centre-of-mass motion of optically trapped spheres was cooled to the quantum ground state for the first time. If the centre-of-mass motion cooled sufficiently, even single collisions with gas molecules can have a noticeable effect and increase the mean occupation number of the oscillator describing the centre-of-mass motion of the sphere.
Current experimental realizations have already achieved a level of control putting them on the verge of resolving such individual kicks. This would not only allow sensing extremely low pressures, but it promises gaining information about the momentum and direction of the scattered gas particles. The present proposal aims to harness this capability to realize a proof-of-principle demonstration of an XHV sensor.
We will investigate the sensor's response to gas collisions as we lower the pressure from moderate, to ultra-high and finally to extreme vacuum. Our sensor should be able to resolve the vacuum pressures required for macroscopic quantum experiments.
In this project, we will place an emphasis on the potential of our sensor's capability for being adapted for the operation in a space environment. Apart from its use for macroscopic quantum experiments, a reliable, space-ready sensor of extremely high vacuum in space could have a range of other applications. Examples are Earth observation,prove a powerful tool for Earth observation, monitoring of space weather or the characterization of the space environment.
Austrian Academy of Sciences - Institute for Quantum Optics and Quantum Information
Austrian Academy of Sciences
Institute for Quantum Optics and Quantum Information
Dr. Rainer Kaltenbaek