Cryo Quantum Lab

In our laboratory we develop and investigate several types of ultrasensitive superconducting and micromechanical devices, with special interest in the application to quantum technologies and fundamental physics. We have available a large dry dilution refrigerator with base temperature 20 mK, equipped with microwave and SQUID instrumentation, a wet dilution refrigerator and several liquid helium cryostats.

Superconducting quantum sensors and devices

We have recently started several projects in the field of superconducting quantum technologies. In particular, we are currently investigating superconducting quantum devices operated in the microwave domain, with focus on parametric amplifiers and single photon detectors. 

Josephson Parametric Amplifiers (JPA)

We are developing flux-pumped Josephson Parametric Amplifiers (JPA), composed of coplanar resonators terminated by a double junction SQUID. We are interested in these devices because of their unique potential as ultralow noise amplifiers of microwave signals, capable of approaching the standard quantum limit (SQL) or even overcoming the SQL when operated in the degenerate phase-sensitive mode. This research is carried out in strict collaboration with FBK (F. Mantegazzini) and CNR-INO (I. Carusotto).

Traveling-wave parametric amplifiers (TWPA)

We have developed traveling-wave parametric amplifiers (TWPA) for broadband and general purpose amplification of microwave signals. In contrast with simple JPAs which are inherently narrowband, TWPAs can be designed as broadband amplifiers, with performance close to the quantum limit over a bandwidth of several GHz. In our group we develop TWPAs based on kinetic inductance nonlinearity, in collaboration with FBK (F. Mantegazzini) and University of Milano Bicocca.

Micromechanics and Quantum Foundations

We have a specific and unique expertise in the field of ultrasensitive detection of weak forces, by means of micromechanical devices cooled to ultralow temperature. We have pioneered a magnetomecanical detection method in which the motion of a microferromagnetic particle is detected by a ultralow noise SQUID. With this method we can measure the very tiny microcantilevers with high quality factor (Q>1E6) down to ultralow temperature (T<50 mK). Initially developed in the context of nanoMRI imaging techniques, this detection method allows to achieve extreme force sensitivity, enabling interesting applications in the context of fundamental physics.

As main achievement, we have performed some of the most stringent tests of wave function spontaneous collapse models, in particular of the most known of these models, the so-called Continuous Spontaneous Localization (CSL). Collapse models have been proposed as a possible solution of the interpretive problems of quantum mechanics, by assuming that the collapse of the wave function is a real effect. In collapse models, the unitary evolution of a quantum system is complemented by a universal mass-proportional dynamical localization mechanism (= collapse in space), encoded by stochastic and nonlinear modifications of the Schrodinger equation. As simplest prediction, this collapse dynamics suppresses quantum superpositions of a massive objects, in contrast with atomic and molecular systems, where superposition states can be observed. However, a common and unavoidable side effect of collapse models is a tiny violation of the energy conservation principle, which can be searched for by means of sensitive mechanical mesurement. By accurately monitoring the motion of an ultraisolated microcantilever at millikelvin temperature, we have indeed set the strongest unambiguous bound on the CSL model to date.

This research is carried out in collaboration with several international partners, in particular Hendrik Ulbricht (University of Southampton), Angelo Bassi (University of Trieste), Tjerk Oosterkamp (University of Leiden).

Levitated magnetomechanics

We can levitate and manipulate tiny micromagnets using a superconducting trap, aiming at exploiting their unique potential as mechanical systems with even lower dissipation. In this context, we have coordinated the EU project LEMAQUME  (LEvitated MAgnets for QUantum MEtrology), funded within the QuantERA Call 2021. The project goal was to realize levitated micromagnets with several different platforms and demonstrate the potential to realize ultrasensitive magnetometers and torque sensors. The project was carried out by a world class consortium, with main partners from Germany (D. Budker, M. Plenio), France (G. Hetet), Israel (R. Folman) and Latvia (A. Cebers), and external partners from UK and US. 

We have already achieved two important milestones: demonstration of ultrasensitive magnetometry and demonstration of gyroscopic coupling between angular degrees of freedom. Furthermore, we have recently managed to spin a micromagnet up to very high frequency (2 MHz) with unprecedented low dissipation. This system holds the promise for precision ultralow torque noise measurements that can be relevant to many fields of fundamental physics (search for axion dark matter, search for ultrahigh-frequency gravitational waves, tests of collapse models and classical gravity models, tests of noninertial quantum effects) and applied physics (pressure sensing, magnetometry, gravimetry, gyroscopes).