The search for Planck scale effects is one of holy grains of physics. At Fermilab, a system of two Michelson interferometers (MIs) was built for this purpose: the holometer. This device operates using classical light, and, therefore, its sensitivity is shot-noise limited. In collaboration with the Danish Technical University, we built a proof of principle experiment devoted to experimentally demonstrate how quantum light could improve the holometer sensitivity below the shot noise limit. It is the first time that quantum light is used in a correlated interferometric system. In particular the injection of two single mode squeezed state (one in each interferometer) and of a twin-beam state is considered, and the system performance compared in the two cases. In this proceeding, after a general introduction to the holometer purposes and to our experimental set-up, we present some characterization measurements concerning the quantum light injection.
Unravelling the mysteries of the complex neural network dynamics of the brain is of utmost importance to science as it might lead to a deeper understanding of perception, cognition and consciousness. Numerous techniques are being used for brain imaging including intracellular electrophysiology, calcium imaging and microelectrode arrays imaging. However, all these technologies are facing severe limitations in the spatio-temporal resolutions and are thus unable to resolve fast real-time single neuron activity over a larger area of the brain. I will discuss our recent efforts in developing a new technique for neuroscience that offer wide-field brain imaging with unprecedented spatio-temporal resolution. It is based on magnetic field sensing of the neuron activity using magneto-optically sensitive Nitrogen-Vacancy color centers in a diamond crystal combined with light microscopy.
Ultra-precise measurements of various parameters such as the mass of nano-particles, magnetic fields or gravity can be attained by probing the phononic modes of a micro-mechanical oscillator with light. The sensitivity of such measurements is in part governed by the noise of the phononic mode as well as the noise of the probing light mode, so by decreasing the noise of the probe beam an enhanced sensitivity can be expected. We demonstrate this effect by using squeezed states of light where the quantum uncertainty of the relevant quadrature is reduced below the shot noise level. Using this squeezing-enhanced sensitivity effect, we demonstrate 1) improved feedback cooling of a phononic mode in a microtoroidal cavity and 2) improved sensing of a magnetic field using the coupling to a microtoroidal phononic mode via a magnetorestrictive material. We present our recent experimental results and discuss future directions.
Since it’s first generation more than 30 years ago, squeezed light has developed towards a tool for high precision measurements as well as a tool for quantum information tasks like quantum key distribution. Miniaturization of sensors is an active field of research with the prospect of many applications. The precision of optical sensors based on interferometric measurements is often limited by the fundamental shot noise. While shot noise can be reduced by increasing the employed light power, integrated sensors pose limitations on the maximum possible amount due to damaging effects of high intensity as well as power consumption. Bright quadrature squeezed light produced by the optical Kerr effect in a nonlinear medium offers an opportunity to overcome these limitations. Here, we present first steps towards a bright quadrature squeezed light source produced by the optical Kerr effect in race-track resonators in silicon nitride by presenting characterizations of the chip. Using standard fabrication techniques this source will have the potential of seamless integration into on-chip optical sensors.
We consider two remote parties connected to a relay by two quantum channels. To generate a secret key, they transmit coherent states to the relay, where the states are subject to a continuous-variable (CV) Bell detection. We study the ideal case where Alice's channel is lossless, i.e., the relay is locally in her lab and the Bell detection is perfomed with unit efficiency. This configuration allows us to explore the optimal performances achievable by CV measurement-device-independent quantum key distribution. This corresponds to the limit of a trusted local relay, where the detection loss can be re-scaled. Our theoretical analysis is confirmed by an experimental simulation where 10-4 secret bits per use can potentially be distributed at 170km assuming ideal reconciliation.
In this contribution, we excite surface plasmon polaritons propagating along a silver nano-wire by a single nitrogenvacancy center located in a diamond nano-crystal. By using the tip of an atomic force microscope, a second nano-wire is brought into the evanescent field of the first wire such that surface plasmons can evanescently couple. In our experiment, we are able to tune the coupling strength from one nano-wire to another by adjusting the gap with the aid of the atomic force microscope. Numerical calculations of the coupling strength are carried out, which support the values found in the experiment.