To understand the fundamental nature of gravity, high-precision interferometers, namely, Holometer (Fermilab), QUEST (Cardiff) and GQuEST (CalTech), seek possible evidence of spacetime fluctuations. These spacetime fluctuations, a feature common to both quantum and semiclassical models of gravity, could be characterised by two-point correlation functions. A two-point correlation function of...
Spontaneous wavefunction collapse models, such as the Continuous Spontaneous Localization (CSL) model, provide a promising approach to address the quantum measurement problem by introducing stochastic, nonlinear modifications to the Schrödinger equation. We present new experimental constraints on the CSL model derived from recent high-precision measurements of optomechanical systems rotational...
A defining signature of classical systems is “in principle measurability” without disturbance: a feature manifestly violated by quantum systems. We describe a multi-interferometer experimental setup that can, in principle, reveal the nonclassicality of a spatial superposition-sourced gravitational field if an irreducible disturbance is caused by a measurement of gravity. While one...
Gravitational-wave observatories such as LIGO and Virgo have enabled a new era in multimessenger astronomy. In recent years, predictions of quantum gravity signatures in interferometers by Craig Hogan, Tom Banks, Eric Verlinde, Frank Wilczek, and Kathryn Zurek have inspired multiple new experiments deploying precision laser interferometry at smaller scales to probe such phenomena, such as the...
We report on the 'QUantum-Enhanced Space-Time experiment' (QUEST), which consists of two co-located Michelson interferometers with the ultimate goal of searching for signatures from the quantization of space-time. We have performed a first engineering run with QUEST which already sets new upper limits for stochastic gravitational waves in the range 13 to 80 MHz, an auxiliary result from the...
How do quantum systems behave in a gravitational field, and what role does operator ordering play in their quantization? This work presents a consistent framework for relativistic quantization, tackling the longstanding operator ordering problem through the introduction of arbitrary constants and by coupling internal quantum and external gravitational degrees of freedom. A general,...
A way to reconcile general relativity and quantum field theory without quantizing the geometry is requiring that the metric evolves stochastically. In this talk, I will first review the main ideas and motivations around hybrid theories that handle the interaction between classical and quantum degrees of freedom in a consistent manner. In the second half of the talk, I will describe how...
I will present the effects of changes in internal energy on gravity-induced entanglement in interference experiments, which in principle allows for faster-than-light communication. By including a change in internal mass-energy due to photon absorption, we show that previous solutions to the thought experiment are insufficient, and we propose new requirements to save causality and...
Relativistic gravitational and many non-gravitational effects are intrinsically weak in their coupling to quantum systems and, therefore, require suitable amplification. To this end, we have identified coherent collections of quantum systems, such as atom arrays, as novel coupling interfaces between relativistic, gravitational, and quantum physics. To illustrate their potential, we shall...
Superpositions of spacetimes have received considerable attention from the Relativistic Quantum Information community. The standard RQI protocol involves calculating the response of an Unruh-DeWitt detector that is coupled to a quantum field whose background spacetime exists in a quantum superposition of geometries. In this work, we propose a method to simulate such a superposition of...
We present a novel approach for detecting the weak gravitational field generated at the Large Hadron Collider (LHC) using cascaded optomechanical cavities. Our methodology exploits coherent averaging to potentially reach Heisenberg-limited sensitivity without entangled resources. In this configuration, $N$ sequentially arranged optomechanical cavities interact with a single laser pulse in the...
Optical clocks based on atoms and ions probe relativistic effects with unprecedented sensitivity by resolving time dilation through frequency shifts. However, all measurements of time dilation so far are effectively classical, stemming from classical motion. Here we show that the first tests of time dilation where the proper time is no longer a single classical parameter can be achieved with...
