Roberto Onofrio - Academia.edu (original) (raw)
Papers by Roberto Onofrio
Journal of Statistical Physics, 2004
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The European Physical Journal B Condensed Matter Physics, Jan 31, 2008
We discuss thermalization of a test particle schematized as a harmonic oscillator and coupled to ... more We discuss thermalization of a test particle schematized as a harmonic oscillator and coupled to a Boltzmann heat bath of finite size and with a finite bandwidth for the frequencies of its particles. We find that complete thermalization only occurs when the test particle frequency is within a certain range of the bath particle frequencies, and for a certain range of mass ratios between the test particle and the bath particles. These results have implications for the study of classical and quantum behaviour of high-frequency nanomechanical resonators.
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Mod Phys Lett a, Jun 2, 1997
Free fall experiments are discussed by using test masses associated to quantum states not necessa... more Free fall experiments are discussed by using test masses associated to quantum states not necessarily possessing a classical counterpart. The times of flight of the Galilean experiments using classical test masses are replaced in the quantum case by probability distributions which, although still not defined in an uncontroversial manner, become manifestly dependent upon the mass and the initial state. Such a dependence is also expected in non-inertial frames of reference if the weak equivalence principle still holds. The latter could be tested, merging recent achievements in mesoscopic physics, by using cooled atoms in free fall and accelerated frames initially prepared in nonclassical quantum states.
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Phys Rev B, 1992
The fundamental sources of noise in a vacuum-tunneling probe used as an electromechanical transdu... more The fundamental sources of noise in a vacuum-tunneling probe used as an electromechanical transducer to monitor the location of a test mass are examined using a first-quantization formalism. We show that a tunneling transducer enforces the Heisenberg uncertainty principle for the position and momentum of a test mass monitored by the transducer through the presence of two sources of noise: the shot noise of the tunneling current and the momentum fluctuations transferred by the tunneling electrons to the test mass. We analyze a number of cases including symmetric and asymmetric rectangular potential barriers and a barrier in which there is a constant electric field. Practical configurations for reaching the quantum limit in measurements of the position of macroscopic bodies with such a class of transducers are studied.
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Aps March Meeting Abstracts, Mar 1, 2007
We have developed an apparatus to assess the thermal effects in Casimir force measurement of a cy... more We have developed an apparatus to assess the thermal effects in Casimir force measurement of a cylinder-plane geometry. Preliminary electrostatic calibrations imply sensitivity sufficient to observe the Casimir force with submicron separation between reflecting surfaces. Work is in progress to improve the sensitivity in order to distinguish the thermal contributions up to 3 microns separation. Another project currently underway at Dartmouth addresses an experimental strategy to verify the dynamical Casimir effect, a dissipative feature of motion in quantum vacuum. In this scheme, Casimir photons generated inside a high-Q cavity with one of the walls driven at GHz frequency [2] would stimulate superradiant emission from ultracold sodium atoms injected into the cavity. We are modeling this system in order to identify the signal features distinguishing Casimir induced superradiance from sodium superflourescence. [1] M. Brown-Hayes, D. A. R Dalvit, F. D. Mazzitelli, W. J. Kim, and R. Onofrio, Phys. Rev. A 72, 051102 (2005). [2] W. J. Kim, J. H. Brownell, and R. Onofrio, Phys. Rev. Lett. 96, 200402 (2006).
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New J Phys, 2003
Contractive states for a free quantum particle were introduced by Yuen (Yuen H P 1983 Phys. Rev. ... more Contractive states for a free quantum particle were introduced by Yuen (Yuen H P 1983 Phys. Rev. Lett. 51 719) in an attempt to evade the standard quantum limit for repeated position measurements. We show how appropriate families of two- and three-component `Schrödinger cat states' are able to support non-trivial correlations between the position and momentum observables leading to contractive behaviour. The existence of contractive Schrödinger cat states is suggestive of potential novel roles of non-classical states for precision measurement schemes.
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Class Quantum Gravity, 2005
We discuss a proposal to measure the Casimir force in the parallel plate configuration in the 1 1... more We discuss a proposal to measure the Casimir force in the parallel plate configuration in the 1 10 µm range via a high-sensitivity torsional balance. This will allow for the measurement of the thermal contribution to the Casimir force thereby discriminating between the various approaches discussed so far. Accurate control of the Casimir force in this length scale is also required to improve the limits to the existence of non-Newtonian forces in the micrometre range predicted by unification models of fundamental interactions.
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Ijmpa, 2010
Macroscopic quantum vacuum and modern theories of gravitation share the strong interplay between ... more Macroscopic quantum vacuum and modern theories of gravitation share the strong interplay between geometry and physical phenomena. We review selected issues related to the accuracy of the measurement of Casimir forces with particular emphasis on the implications for the search of non-Newtonian gravitational forces in the micrometer range. We then discuss the interplay of the Higgs particle with gravitation, arguing that spectroscopic shifts in atomic transitions due to the modifications of the vacuum expectation value of the Higgs field in regions with strong curvature of space-time may be of conceptual and observational relevance.
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Physical Review a General Physics, Feb 1, 1990
A technique is proposed to improve the squeezing of the mechanical noise in a back-action evasion... more A technique is proposed to improve the squeezing of the mechanical noise in a back-action evasion measurement. The scheme is based on the use of a parametric multipump system and, in the limit of many pump components, approaches a stroboscopic measurement. A simple model of the back-action evasion effect for this scheme is developed. Experimental evidence of a significant increase in the squeezing with respect to the two-pump scheme and in accordance with the model is reported.
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Phys Rev D, 1997
Free fall in a uniform gravitational field is reexamined in the case of quantum states with and w... more Free fall in a uniform gravitational field is reexamined in the case of quantum states with and without a classical analogue. The interplay between kinematics and dynamics in the evolution of a falling quantum test particle is discussed allowing for a better understanding of the equivalence principle at the operational level.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
We propose an electromechanical transducer based on a resonant-tunneling configuration that, with... more We propose an electromechanical transducer based on a resonant-tunneling configuration that, with respect to the standard tunneling transducers, allows larger tunneling currents while using the same bias voltage. The increased current leads to an increase of the shot noise and an increase of the momentum noise which determine the quantum limit in the system under monitoring. Experiments with micromachined masses at 4.2 K could show dominance of the momentum noise over the Brownian noise, allowing observation of the quantum-mechanical noise at the mesoscopic scale.
Bookmarks Related papers MentionsView impact
We discuss a model of repeated measurements of position in a quantum system which is monitored fo... more We discuss a model of repeated measurements of position in a quantum system which is monitored for a finite amount of time with a finite instrumental error. In this framework we recover the optimum monitoring of a harmonic oscillator proposed in the case of an instantaneous collapse of the wavefunction into an infinite-accuracy measurement result. We also establish numerically the existence of an optimal measurement strategy in the case of a nonlinear system. This optimal strategy is completely defined by the spectral properties of the nonlinear system.
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Physical Review a, May 1, 1997
The measurement process is taken into account in the dynamics of trapped ions prepared in nonclas... more The measurement process is taken into account in the dynamics of trapped ions prepared in nonclassical motional states. The induced decoherence is shown to manifest itself both in the inhibition of the internal population dynamics and in a damping of the vibrational motion without classical counterpart. Quantitative comparison with present experimental capabilities is discussed, leading to a proposal for the verification of the predicted effects.
Bookmarks Related papers MentionsView impact
Contractive states for a free quantum particle were introduced by Yuen [Yuen H P 1983 Phys. Rev. ... more Contractive states for a free quantum particle were introduced by Yuen [Yuen H P 1983 Phys. Rev. Lett. 51, 719] in an attempt to evade the standard quantum limit for repeated position measurements. We show how appropriate families of two- and three component ``Schroedinger cat states'' are able to support non-trivial correlations between the position and momentum observables leading to contractive behavior. The existence of contractive Schroedinger cat states is suggestive of potential novel roles of non-classical states for precision measurement schemes.
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Laser Phys, 2007
We describe an experimental setup designed to produce ultracold trapped gas clouds of fermionic 6... more We describe an experimental setup designed to produce ultracold trapped gas clouds of fermionic 6Li and bosonic 87Rb. This combination of alkali metals has the potential to reach deeper Fermi degeneracy with respect to other mixtures since it allows for improved heat capacity matching which optimizes sympathetic cooling efficiency. Atomic beams of the two species are independently produced and then decelerated by Zeeman slowers. The slowed atoms are collected into a magneto-optical trap and then transferred into a quadrupole magnetic trap. An ultracold Fermi gas with temperature in the 10^-3 T_F range should be attainable through selective confinement of the two species via a properly detuned laser beam focused in the center of the magnetic trap.
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Physical Review Letters, 1999
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A review of current efforts to approach and to surpass the fundamental limit in the sensitivity o... more A review of current efforts to approach and to surpass the fundamental limit in the sensitivity of the Weber type gravitational wave antennae is reported. Applications of quantum non-demolition techniques to the concrete example of an antenna resonant with the transducer are discussed in detail. Analogies and differences from the framework of the squeezed states in quantum optics are discussed.
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We have performed numerical simulations to evaluate the effect on the capacitance of finite size ... more We have performed numerical simulations to evaluate the effect on the capacitance of finite size boundaries realistically present in the parallel plane, sphere-plane, and cylinder-plane geometries. The potential impact of edge effects in assessing the accuracy of the parameters obtained in the electrostatic calibrations of Casimir force experiments is then discussed.
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Phys Rev a, 2005
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Journal of Statistical Physics, 2004
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The European Physical Journal B Condensed Matter Physics, Jan 31, 2008
We discuss thermalization of a test particle schematized as a harmonic oscillator and coupled to ... more We discuss thermalization of a test particle schematized as a harmonic oscillator and coupled to a Boltzmann heat bath of finite size and with a finite bandwidth for the frequencies of its particles. We find that complete thermalization only occurs when the test particle frequency is within a certain range of the bath particle frequencies, and for a certain range of mass ratios between the test particle and the bath particles. These results have implications for the study of classical and quantum behaviour of high-frequency nanomechanical resonators.
Bookmarks Related papers MentionsView impact
Mod Phys Lett a, Jun 2, 1997
Free fall experiments are discussed by using test masses associated to quantum states not necessa... more Free fall experiments are discussed by using test masses associated to quantum states not necessarily possessing a classical counterpart. The times of flight of the Galilean experiments using classical test masses are replaced in the quantum case by probability distributions which, although still not defined in an uncontroversial manner, become manifestly dependent upon the mass and the initial state. Such a dependence is also expected in non-inertial frames of reference if the weak equivalence principle still holds. The latter could be tested, merging recent achievements in mesoscopic physics, by using cooled atoms in free fall and accelerated frames initially prepared in nonclassical quantum states.
Bookmarks Related papers MentionsView impact
Phys Rev B, 1992
The fundamental sources of noise in a vacuum-tunneling probe used as an electromechanical transdu... more The fundamental sources of noise in a vacuum-tunneling probe used as an electromechanical transducer to monitor the location of a test mass are examined using a first-quantization formalism. We show that a tunneling transducer enforces the Heisenberg uncertainty principle for the position and momentum of a test mass monitored by the transducer through the presence of two sources of noise: the shot noise of the tunneling current and the momentum fluctuations transferred by the tunneling electrons to the test mass. We analyze a number of cases including symmetric and asymmetric rectangular potential barriers and a barrier in which there is a constant electric field. Practical configurations for reaching the quantum limit in measurements of the position of macroscopic bodies with such a class of transducers are studied.
Bookmarks Related papers MentionsView impact
Aps March Meeting Abstracts, Mar 1, 2007
We have developed an apparatus to assess the thermal effects in Casimir force measurement of a cy... more We have developed an apparatus to assess the thermal effects in Casimir force measurement of a cylinder-plane geometry. Preliminary electrostatic calibrations imply sensitivity sufficient to observe the Casimir force with submicron separation between reflecting surfaces. Work is in progress to improve the sensitivity in order to distinguish the thermal contributions up to 3 microns separation. Another project currently underway at Dartmouth addresses an experimental strategy to verify the dynamical Casimir effect, a dissipative feature of motion in quantum vacuum. In this scheme, Casimir photons generated inside a high-Q cavity with one of the walls driven at GHz frequency [2] would stimulate superradiant emission from ultracold sodium atoms injected into the cavity. We are modeling this system in order to identify the signal features distinguishing Casimir induced superradiance from sodium superflourescence. [1] M. Brown-Hayes, D. A. R Dalvit, F. D. Mazzitelli, W. J. Kim, and R. Onofrio, Phys. Rev. A 72, 051102 (2005). [2] W. J. Kim, J. H. Brownell, and R. Onofrio, Phys. Rev. Lett. 96, 200402 (2006).
Bookmarks Related papers MentionsView impact
New J Phys, 2003
Contractive states for a free quantum particle were introduced by Yuen (Yuen H P 1983 Phys. Rev. ... more Contractive states for a free quantum particle were introduced by Yuen (Yuen H P 1983 Phys. Rev. Lett. 51 719) in an attempt to evade the standard quantum limit for repeated position measurements. We show how appropriate families of two- and three-component `Schrödinger cat states' are able to support non-trivial correlations between the position and momentum observables leading to contractive behaviour. The existence of contractive Schrödinger cat states is suggestive of potential novel roles of non-classical states for precision measurement schemes.
Bookmarks Related papers MentionsView impact
Class Quantum Gravity, 2005
We discuss a proposal to measure the Casimir force in the parallel plate configuration in the 1 1... more We discuss a proposal to measure the Casimir force in the parallel plate configuration in the 1 10 µm range via a high-sensitivity torsional balance. This will allow for the measurement of the thermal contribution to the Casimir force thereby discriminating between the various approaches discussed so far. Accurate control of the Casimir force in this length scale is also required to improve the limits to the existence of non-Newtonian forces in the micrometre range predicted by unification models of fundamental interactions.
Bookmarks Related papers MentionsView impact
Ijmpa, 2010
Macroscopic quantum vacuum and modern theories of gravitation share the strong interplay between ... more Macroscopic quantum vacuum and modern theories of gravitation share the strong interplay between geometry and physical phenomena. We review selected issues related to the accuracy of the measurement of Casimir forces with particular emphasis on the implications for the search of non-Newtonian gravitational forces in the micrometer range. We then discuss the interplay of the Higgs particle with gravitation, arguing that spectroscopic shifts in atomic transitions due to the modifications of the vacuum expectation value of the Higgs field in regions with strong curvature of space-time may be of conceptual and observational relevance.
Bookmarks Related papers MentionsView impact
Physical Review a General Physics, Feb 1, 1990
A technique is proposed to improve the squeezing of the mechanical noise in a back-action evasion... more A technique is proposed to improve the squeezing of the mechanical noise in a back-action evasion measurement. The scheme is based on the use of a parametric multipump system and, in the limit of many pump components, approaches a stroboscopic measurement. A simple model of the back-action evasion effect for this scheme is developed. Experimental evidence of a significant increase in the squeezing with respect to the two-pump scheme and in accordance with the model is reported.
Bookmarks Related papers MentionsView impact
Phys Rev D, 1997
Free fall in a uniform gravitational field is reexamined in the case of quantum states with and w... more Free fall in a uniform gravitational field is reexamined in the case of quantum states with and without a classical analogue. The interplay between kinematics and dynamics in the evolution of a falling quantum test particle is discussed allowing for a better understanding of the equivalence principle at the operational level.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
We propose an electromechanical transducer based on a resonant-tunneling configuration that, with... more We propose an electromechanical transducer based on a resonant-tunneling configuration that, with respect to the standard tunneling transducers, allows larger tunneling currents while using the same bias voltage. The increased current leads to an increase of the shot noise and an increase of the momentum noise which determine the quantum limit in the system under monitoring. Experiments with micromachined masses at 4.2 K could show dominance of the momentum noise over the Brownian noise, allowing observation of the quantum-mechanical noise at the mesoscopic scale.
Bookmarks Related papers MentionsView impact
We discuss a model of repeated measurements of position in a quantum system which is monitored fo... more We discuss a model of repeated measurements of position in a quantum system which is monitored for a finite amount of time with a finite instrumental error. In this framework we recover the optimum monitoring of a harmonic oscillator proposed in the case of an instantaneous collapse of the wavefunction into an infinite-accuracy measurement result. We also establish numerically the existence of an optimal measurement strategy in the case of a nonlinear system. This optimal strategy is completely defined by the spectral properties of the nonlinear system.
Bookmarks Related papers MentionsView impact
Physical Review a, May 1, 1997
The measurement process is taken into account in the dynamics of trapped ions prepared in nonclas... more The measurement process is taken into account in the dynamics of trapped ions prepared in nonclassical motional states. The induced decoherence is shown to manifest itself both in the inhibition of the internal population dynamics and in a damping of the vibrational motion without classical counterpart. Quantitative comparison with present experimental capabilities is discussed, leading to a proposal for the verification of the predicted effects.
Bookmarks Related papers MentionsView impact
Contractive states for a free quantum particle were introduced by Yuen [Yuen H P 1983 Phys. Rev. ... more Contractive states for a free quantum particle were introduced by Yuen [Yuen H P 1983 Phys. Rev. Lett. 51, 719] in an attempt to evade the standard quantum limit for repeated position measurements. We show how appropriate families of two- and three component ``Schroedinger cat states'' are able to support non-trivial correlations between the position and momentum observables leading to contractive behavior. The existence of contractive Schroedinger cat states is suggestive of potential novel roles of non-classical states for precision measurement schemes.
Bookmarks Related papers MentionsView impact
Laser Phys, 2007
We describe an experimental setup designed to produce ultracold trapped gas clouds of fermionic 6... more We describe an experimental setup designed to produce ultracold trapped gas clouds of fermionic 6Li and bosonic 87Rb. This combination of alkali metals has the potential to reach deeper Fermi degeneracy with respect to other mixtures since it allows for improved heat capacity matching which optimizes sympathetic cooling efficiency. Atomic beams of the two species are independently produced and then decelerated by Zeeman slowers. The slowed atoms are collected into a magneto-optical trap and then transferred into a quadrupole magnetic trap. An ultracold Fermi gas with temperature in the 10^-3 T_F range should be attainable through selective confinement of the two species via a properly detuned laser beam focused in the center of the magnetic trap.
Bookmarks Related papers MentionsView impact
Physical Review Letters, 1999
Bookmarks Related papers MentionsView impact
A review of current efforts to approach and to surpass the fundamental limit in the sensitivity o... more A review of current efforts to approach and to surpass the fundamental limit in the sensitivity of the Weber type gravitational wave antennae is reported. Applications of quantum non-demolition techniques to the concrete example of an antenna resonant with the transducer are discussed in detail. Analogies and differences from the framework of the squeezed states in quantum optics are discussed.
Bookmarks Related papers MentionsView impact
We have performed numerical simulations to evaluate the effect on the capacitance of finite size ... more We have performed numerical simulations to evaluate the effect on the capacitance of finite size boundaries realistically present in the parallel plane, sphere-plane, and cylinder-plane geometries. The potential impact of edge effects in assessing the accuracy of the parameters obtained in the electrostatic calibrations of Casimir force experiments is then discussed.
Bookmarks Related papers MentionsView impact
Phys Rev a, 2005
Bookmarks Related papers MentionsView impact