## About

116

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Introduction

Additional affiliations

June 2009 - present

January 2002 - December 2004

January 2001 - December 2005

## Publications

Publications (116)

The precision of optical atomic clocks is approaching a regime where they resolve gravitational time dilation on smaller scales than their own extensions. Hence, an accurate description of quantum clocks has to take their spatial extension into account. In this article, as a first step towards a fully relativistic description of extended quantum cl...

Concerted efforts are underway to establish an infrastructure for a global quantum internet to realise a spectrum of quantum technologies. This will enable more precise sensors, secure communications, and faster data processing. Quantum communications are a front-runner with quantum networks already implemented in several metropolitan areas. A numb...

We develop a method for computing the Bogoliubov transformation experienced by a confined quantum scalar field in a globally hyperbolic spacetime, due to the changes in the geometry and/or the confining boundaries. The method constructs a basis of solutions to the Klein-Gordon equation associated to each compact Cauchy hypersurface of constant time...

We develop a method for computing the Bogoliubov transformation experienced by a confined quantum scalar field in a globally hyperbolic spacetime, due to the changes in the geometry and/or the confining boundaries. The method constructs a basis of solutions to the Klein-Gordon equation associated to each compact Cauchy hypersurface of constant time...

Concerted efforts are underway to establish an infrastructure for a global quantum internet to realise a spectrum of quantum technologies. This will enable more precise sensors, secure communications, and faster data processing. Quantum communications are a front-runner with quantum networks already implemented in several metropolitan areas. A numb...

We introduce a quantum interferometric scheme that uses states that are sharp in frequency and delocalized in position. The states are frequency modes of a quantum field that is trapped at all times in a finite volume potential, such as a small box potential. This allows for significant miniaturization of interferometric devices. Since the modes ar...

We study the time evolution of an ideal system composed of two harmonic oscillators coupled through a quadratic Hamiltonian with arbitrary interaction strength. We solve its dynamics analytically by employing tools from symplectic geometry. In particular, we use this result to completely characterize the dynamics of the two oscillators interacting...

We develop a method for computing the Bogoliubov transformation experienced by a confined quantum scalar field in a globally hyperbolic spacetime, due to the changes in the geometry and/or the confining boundaries. The method constructs a basis of modes of the field associated to each Cauchy hypersurface, by means of an eigenvalue problem posed in...

We investigate the quantum thermodynamical properties of localised relativistic quantum fields, and how they can be used as quantum thermal machines. We study the efficiency and power of energy transfer between the classical gravitational degrees of freedom, such as the energy input due to the motion of boundaries or an impinging gravitational wave...

Gravity gradiometry with Bose-Einstein condensates (BECs) has reached unprecedented precisions. The basis of this technique is the measurement of differential forces by interference of single-atom wave functions. In this article, we propose a gradiometry scheme where phonons, the collective oscillations of a trapped BEC's atoms are used instead. We...

We study the time evolution of an ideal system composed of two harmonic oscillators coupled through a quadratic Hamiltonian with arbitrary interaction strength. We solve the dynamics analytically by employing Lie algebraic tools that allow to decouple the time-evolution operator induced by quadratic Hamiltonians. In particular, we use this result t...

We propose an experiment based on a Bose-Einstein condensate interferometer for strongly constraining fifth-force models. Additional scalar fields from modified gravity or higher dimensional theories may account for dark energy and the accelerating expansion of the Universe. These theories have led to proposed screening mechanisms to fit within the...

Additional scalar fields from scalar-tensor, modified gravity or higher dimensional theories beyond general relativity may account for dark energy and the accelerating expansion of the Universe. These theories have led to proposed models of screening mechanisms, such as chameleon and symmetron fields, to account for the tight experimental bounds on...

Despite almost a century worth of study, it is still unclear how general relativity (GR) and quantum theory (QT) should be unified into a consistent theory. The conventional approach is to retain the foundational principles of QT, such as the superposition principle, and modify GR. This is referred to as 'quantizing gravity', resulting in a theory...

We consider an interferometer that contains active elements, such as a parametric amplifier, with general two-mode Gaussian unitary channels rather than the usually considered phase-shift channel. We concentrate on a scheme based on the recently proposed pumped-up SU(1,1) active interferometer where all input particles participate in the parameter...

Quantum theory and relativity offer different conceptions of time. To explore the conflict between them, we study a quantum version of the light-clock commonly used to illustrate relativistic time dilation. This semiclassical model combines elements of both theories. We show for Gaussian states of the light field that the clock times are independen...

Despite almost a century worth of study, it is still unclear how general relativity (GR) and quantum theory (QT) should be unified into a consistent theory. The conventional approach is to retain the foundational principles of QT, such as the superposition principle, and modify GR. This is referred to as 'quantizing gravity', resulting in a theory...

A gravitational-wave (GW) detector that utilizes the phononic excitations of a Bose-Einstein condensate (BEC) has recently been proposed [NJP 16, 085003 (2014)]. A subsequent and independent study, [arXiv:1807.07046], has suggested an alternative GW detection scheme that also uses phonons of a BEC but which was found to be many orders of magnitude...

We develop a method for computing the evolution of a quantum real Klein-Gordon field in a region of spacetime. The method is both of general applicability and particularly useful in certain important problems, such as the study of confined quantum fields under small perturbations. Instead of computing the evolution of the initial state of the field...

We consider schemes where quantum optical signals are exchanged between a source on Earth and a satellite. The curved spacetime background changes the quantum state of the photons. We employ quantum metrology techniques to obtain optimal bounds for the precision of the quantum measurements of relevant physical parameters encoded in the final state....

Additional scalar fields from scalar-tensor, modified gravity or higher dimensional theories beyond general relativity may account for dark energy and the accelerating expansion of the Universe. These theories have lead to proposed models of screening mechanisms, such as chameleon and symmetron fields, to account for the tight experimental bounds o...

We study relativistic effects on polarised photons that travel in a curved spacetime. As a concrete application, we specialise to photons propagating in the gravitational field of the Earth between a laboratory and satellites. We show that wave packets of light initially in quantum superpositions of momentum-helicity states acquire Wigner phases as...

A description of the dynamical response of uniformly trapped Bose-Einstein condensates (BECs) to oscillating external gravitational fields is developed, with the inclusion of damping. Two different effects that can lead to the creation of phonons in the BEC are identified; direct driving and parametric driving. Additionally, the oscillating gravita...

Models of quantum systems on curved space-times lack sufficient experimental verification. Some speculative theories suggest that quantum correlations, such as entanglement, may exhibit different behavior to purely classical correlations in curved space. By measuring this effect or lack thereof, we can test the hypotheses behind several such models...

The effect of gravity and proper acceleration on the frequency spectrum of an optical resonator - both rigid or deformable - is considered in the framework of general relativity. The optical resonator is modeled either as a rod of matter connecting two mirrors or as a dielectric rod whose ends function as mirrors. Explicit expressions for the frequ...

A description of the dynamical response of uniformly trapped Bose-Einstein condensates (BECs) to oscillating external gravitational fields is developed, with the inclusion of damping. Two different effects that can lead to the creation of phonons in the BEC are identified; direct driving and parametric driving. Additionally, the oscillating gravita...

We apply recently developed techniques from quantum optics and quantum information science to Bose-Einstein Condensates (BECs) in order to study the quantum decoherence of phonons of isolated BECs. In the last few years, major advances in the manipulation and control of phonons have highlighted their potential as carriers of quantum information in...

The recent detections of gravitational waves (GWs) by the LIGO and Virgo collaborations have opened the field of GW astronomy, intensifying interest in GWs and other possible detectors sensitive in different frequency ranges. Although strong GW producing events are rare and currently unpredictable, GWs can in principle be simulated in analogue syst...

The conflict between quantum theory and the theory of relativity is exemplified in their treatment of time. We examine the ways in which their conceptions differ, and describe a semiclassical clock model combining elements of both theories. The results obtained with this clock model in flat spacetime are reviewed, and the problem of generalizing th...

The video shows the impact of the crate source on the drop tower experiment with different playback speeds.

The video shows how the centrifuge accelerates with the crate source to 30g.

We study how quantum systems that propagate in the spacetime of a rotating planet are affected by the curved background. Spacetime curvature affects wavepackets of photons propagating from Earth to a satellite, and the changes in the wavepacket encode the parameters of the spacetime. This allows us to evaluate quantitatively how quantum communicati...

Models of quantum systems on curved space-times lack sufficient experimental verification. Some speculative theories suggest that quantum properties, such as entanglement, may exhibit entirely different behavior to purely classical systems. By measuring this effect or lack thereof, we can test the hypotheses behind several such models. For instance...

The conflict between quantum theory and the theory of relativity is exemplified in their treatment of time. We examine the ways in which their conceptions differ, and describe a semiclassical clock model combining elements of both theories. The results obtained with this clock model in flat spacetime are reviewed, and the problem of generalizing th...

The quantization of the electromagnetic field has successfully paved the way for the development of the Standard Model of Particle Physics and has established the basis for quantum technologies. Gravity, however, continues to hold out against physicists' efforts of including it into the framework of quantum theory. Experimental techniques in quantu...

At the beginning of the previous century, Newtonian mechanics fell victim to two new revolutionary theories, Quantum Mechanics (QM) and General Relativity (GR). Both theories have transformed our view of physical phenomena, with QM accurately predicting the results of experiments taking place at small length scales, and GR correctly describing obse...

We investigate the quantum thermodynamical properties of localised relativistic quantum fields that can be used as quantum thermal machines. We study the efficiency and power of energy transfer between the classical degrees of freedom, such as the energy input due to motion or to an impinging gravitational wave, and the excitations of the confined...

We construct a practical method for finding optimal Gaussian probe states for the estimation of parameters encoded by Gaussian unitary channels. This method can be used for finding all optimal probe states, rather than focussing on the performance of specific states as shown in previous studies. As an example, we apply this method to find optimal p...

We investigate the thermodynamical properties of quantum fields in curved
spacetime. Our approach is to consider quantum fields in curved spacetime as a
quantum system undergoing an out-of-equilibrium transformation. The
non-equilibrium features are studied by using a formalism which has been
developed to derive fluctuation relations and emergent i...

We employ quantum estimation techniques to obtain ultimate bounds on
precision measurements of gravitational parameters of the spacetime outside a
rotating planet. Spacetime curvature affects the frequency distribution of a
photon sent from Earth to a satellite, and this change encodes parameters of
the spacetime. This allows us to achieve precise...

Relativistic quantum metrology provides an optimal strategy for the
estimation of parameters encoded in quantum fields in flat and curved
spacetime. These parameters usually correspond to physical quantities of
interest such as proper times, accelerations, gravitational field strengths,
among other spacetime parameters. The precise estimation of th...

Moving cavities promise to be a suitable system for relativistic quantum
information processing. It has been shown that an inertial and a uniformly
accelerated one-dimensional cavity can become entangled by letting an atom emit
an excitation while it passes through the cavities, but the acceleration
degrades the ability to generate entanglement. We...

Gaussian states are of increasing interest in the estimation of physical
parameters because they are easy to prepare and manipulate in experiments. In
this article, we derive formulae for the optimal estimation of parameters using
two- and multi-mode Gaussian states. As an application of our result, we derive
the optimal Gaussian probe states for t...

Quasiparticles in a Bose-Einstein condensate are sensitive to space-time
distortions. Gravitational waves can induce transformations on the state of
phonons that can be observed through quantum state discrimination techniques.
We show that this method is highly robust to thermal noise and depletion. We
derive a bound on the strain sensitivity that...

Quantum metrology studies quantum strategies which enable us to outperform their classical counterparts. In this framework, the existence of perfect classical reference frames is usually assumed. However, such ideal reference frames might not always be available. The reference frames required in metrology strategies can either degrade or become mis...

We address the issue of precisely estimating small parameters encoded in a
general linear transformation of the modes of a bosonic quantum field. Such
Bogoliubov transformations frequently appear in the context of quantum optics.
We provide a recipe for computing the quantum Fisher information for arbitrary
pure initial states. We show that the max...

We analyse the generation of quantum discord by means of the dynamical
Casimir effect in superconducting waveguides modulated by superconducting
quantum interferometric devices. We show that for realistic experimental
parameters, the conditions for the existence of quantum discord are less
demanding than the previously considered for quantum entang...

We introduce a primary thermometer which measures the temperature of a Bose-Einstein Condensate in the sub-nK regime. We show, using quantum Fisher information, that the precision of our technique improves the state-of-the-art in thermometry in the sub-nK regime. The temperature of the condensate is mapped onto the quantum phase of an atomic dot th...

We show that motion and gravity affect the precision of quantum clocks. We
consider a localised quantum field as a fundamental model of a quantum clock
moving in spacetime and show that its state is modified due to changes in
acceleration. By computing the quantum Fisher information we determine how
relativistic motion modifies the ultimate bound i...

We propose a quantum experiment to measure with high precision the
Schwarzschild space-time parameters of the Earth. The scheme can also be
applied to measure distances by taking into account the curvature of the
Earth's space-time. As a wave-packet of (entangled) light is sent from the
Earth to a satellite it is red-shifted and deformed due to the...

We show that gravitational waves create phonons in a Bose-Einstein condensate
(BEC). A traveling spacetime distortion produces particle creation resonances
that correspond to the dynamical Casimir effect in a BEC phononic field
contained in a cavity-type trap. We propose to use this effect to detect
gravitational waves. The amplitude of the wave ca...

We study the effects of three-body collisions in the basic physical
properties of a two-mode Bose-Einstein condensate. By finding the exact
analytical solution of a model which includes two-body and three-body elastic
and mode-exchange collisions, we show analytically that three-body interactions
produce observable effects in the probability distri...

We introduce a microscopic computation which shows that the Hamiltonian of a
Bose-Einstein Condensate can be analytically solved in the two-mode
approximation, in particular, in the case of an asymmetric double-well
condensate in the dilute regime. Our model is exactly diagonalisable when the
overlap of the quasilocalized modes in each well is smal...

We show how to vary the physical properties of a Bose-Einstein condensate
(BEC) in order to mimic an effective gravitational-wave spacetime. In
particular, we focus in the simulation of the recently discovered creation of
particles by real spacetime distortion in box-type traps. We show that, by
modulating the speed of sound in the BEC, the phonons...

We present a framework for relativistic quantum metrology that is useful for
both Earth-based and space-based technologies. Quantum metrology has been so
far successfully applied to design precision instruments such as clocks and
sensors which outperform classical devices by exploiting quantum properties.
There are advanced plans to implement these...

We show that particle creation of Bogoliubov modes in a Bose-Einstein
condensate due to the accelerated motion of the trap is a genuinely
relativistic effect. To this end we show that Bogoliubov modes can be described
by a time rescaling of the Minkowski metric. A consequence of this is that
Rindler transformations are perceived by the phonons as g...

We propose an experiment to test the effects of gravity and acceleration on
quantum entanglement in space-based setups. We show that the entanglement
between excitations of two Bose-Einstein condensates is degraded after one of
them undergoes a change in the gravitational field strength. This prediction
can be tested if the condensates are initiall...

Experimental searches for the thermal radiation from analogue black holes
require the measurement of very low temperatures in regimes where other thermal
noises may interfere or even mimic the sought-after effect. In this letter, we
parameterize the family of bosonic thermal channels which give rise to such
thermal effects and show that by use of c...

In quantum metrology quantum properties such as squeezing and entanglement
are exploited in the design of a new generation of clocks, sensors and other
measurement devices that can outperform their classical counterparts.
Applications of great technological relevance lie in the precise measurement of
parameters which play a central role in relativi...

We investigate the intrinsic uncertainty in the accuracy to which a static
spacetime can be measured from scattering experiments. In particular, we focus
on the Schwarzschild black hole and a spatially kinked metric that has some
mathematical resemblance to an expanding universe. Under selected conditions we
find that the scattering problem can be...

Time dilation, a striking prediction of Einstein's relativity, plays an
important role in applications such as the Global Positioning System. One of
the most compelling consequences of time dilation is known as the twin paradox,
where a twin at rest ages more than her sibling travelling at relativistic
speeds. In this paper, we propose an implement...

We show how to use relativistic motion to generate continuous variable
Gaussian cluster states within cavity modes. Our results can be demonstrated
experimentally using superconducting circuits where tunable boundary conditions
correspond to mirrors moving with velocities close to the speed of light. In
particular, we propose the generation of a qu...

We investigate the possibility to generate quantum-correlated quasi-particles
utilizing analogue gravity systems. The quantumness of these correlations is a
key aspect of analogue gravity effects and their presence allows for a clear
separation between classical and quantum analogue gravity effects. However,
experiments in analogue systems, such as...

We investigate the effects of space-time curvature on space-based quantum
communication protocols. We analyze tasks that require either the exchange of
single photons in a certain entanglement distribution protocol or beams of
light in a continuous-variable quantum key distribution scheme. We find that
gravity affects the propagation of photons, th...

We show that the relativistic motion of a quantum system can be used to generate quantum gates. The nonuniform acceleration of a cavity is used to generate well-known two-mode quantum gates in continuous variables. Observable amounts of entanglement between the cavity modes are produced through resonances that appear by repeating periodically any t...

We show that mode-mixing quantum gates can be produced by non-uniform
relativistic acceleration. Periodic motion in cavities exhibits a series of
resonant conditions producing entangling quantum gates between different
frequency modes. The resonant condition associated with particle creation is
the main feature of the dynamical Casimir effect which...

We show how Berry phase can be used to construct an ultra-high precision
quantum thermometer. An important advantage of our scheme is that there is no
need for the thermometer to acquire thermal equilibrium with the sample. This
reduces measurement times and avoids precision limitations.

The techniques employed to solve the interaction of a detector and a quantum
field typically require perturbation methods. We introduce mathematical
techniques to solve the time evolution of an arbitrary number of detectors
interacting with a quantum field. Our techniques apply to harmonic oscillator
detectors and can be generalized to treat detect...

We study the effects of relativistic motion on quantum teleportation and
propose a realizable experiment where our results can be tested. We compute
bounds on the optimal fidelity of teleportation when one of the observers
undergoes non-uniform motion for a finite time. The upper bound to the optimal
fidelity is degraded due to the observer's motio...