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Tobias Donner - One of the best experts on this subject based on the ideXlab platform.
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Continuous feedback on a Quantum Gas coupled to an optical cavity
New Journal of Physics, 2020Co-Authors: Katrin Kroeger, Tobias Donner, Nishant Dogra, Rodrigo Rosa-medina, Marcin Paluch, Francesco Ferri, Tilman EsslingerAbstract:We present an active feedback scheme acting continuously on the state of a Quantum Gas dispersively coupled to a high-finesse optical cavity. The Quantum Gas is subject to a transverse pump laser field inducing a self-organization phase transition, where the Gas acquires a density modulation and photons are scattered into the resonator. Photons leaking from the cavity allow for a real-time and non-destructive readout of the system. We stabilize the mean intra-cavity photon number through a micro-processor controlled feedback architecture acting on the intensity of the transverse pump field. The feedback scheme can keep the mean intra-cavity photon number $n_\text{ph}$ constant, in a range between $n_\text{ph}=0.17\pm 0.04$ and $n_\text{ph}=27.6\pm 0.5$, and for up to 4 s. Thus we can engage the stabilization in a regime where the system is very close to criticality as well as deep in the self-organized phase. The presented scheme allows us to approach the self-organization phase transition in a highly controlled manner and is a first step on the path towards the realization of many-body phases driven by tailored feedback mechanisms.
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Coupling two order parameters in a Quantum Gas
Nature Materials, 2018Co-Authors: Andrea Morales, Tilman Esslinger, Philip Zupancic, Julian Léonard, Tobias DonnerAbstract:Ultracold atoms can model single-order Quantum phases, but coupling of different order parameters has not been shown. Here, this is demonstrated using two optical resonators, facilitating exploration of multiple-order systems such as multiferroics. Controlling matter to simultaneously support coupled properties is of fundamental and technological importance^ 1 (for example, in multiferroics^ 2 – 5 or high-temperature superconductors^ 6 – 9 ). However, determining the microscopic mechanisms responsible for the simultaneous presence of different orders is difficult, making it hard to predict material phenomenology^ 10 , 11 or modify properties^ 12 – 16 . Here, using a Quantum Gas to engineer an adjustable interaction at the microscopic level, we demonstrate scenarios of competition, coexistence and mutual enhancement of two orders. For the enhancement scenario, the presence of one order lowers the critical point of the other. Our system is realized by a Bose–Einstein condensate that can undergo self-organization phase transitions in two optical resonators^ 17 , resulting in two distinct crystalline density orders. We characterize the coupling between these orders by measuring the composite order parameter and the elementary excitations and explain our results with a mean-field free-energy model derived from a microscopic Hamiltonian. Our system is ideally suited to explore Quantum tricritical points^ 18 and can be extended to study the interplay of spin and density orders^ 19 as a function of temperature^ 20 .
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Coupling two order parameters in a Quantum Gas
Nature materials, 2018Co-Authors: Andrea Morales, Tilman Esslinger, Philip Zupancic, Julian Léonard, Tobias DonnerAbstract:Controlling matter to simultaneously support multiple coupled properties is of fundamental and technological importance. For example, the simultaneous presence of magnetic and ferroelectric orders in multiferroic materials leads to enhanced functionalities. In high-temperature superconductors, intertwining between charge- and spin-order can form superconducting states at high transition temperatures. However, pinning down the microscopic mechanisms responsible for the simultaneous presence of different orders is difficult, making it hard to predict the phenomenology of a material or to experimentally modify its properties. Here we use a Quantum Gas to engineer an adjustable interaction at the microscopic level between two orders, and demonstrate scenarios of competition, coexistence and coupling between them. In the latter case, intriguingly, the presence of one order lowers the critical point of the other. Our system is realized by a Bose-Einstein condensate which can undergo self-organization phase transitions in two optical resonators, resulting in two distinct crystalline density orders. We characterize the intertwining between these orders by measuring the composite order parameter and the elementary excitations. We explain our results with a mean-field free energy model, which is derived from a microscopic Hamiltonian. Our system is ideally suited to explore properties of Quantum tricritical points as recently realized in and can be extended to study the interplay of spin and density orders also as a function of temperature.
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coupling two order parameters in a Quantum Gas
Nature Materials, 2018Co-Authors: Andrea Morales, Tilman Esslinger, Philip Zupancic, Julian Léonard, Tobias DonnerAbstract:Controlling matter to simultaneously support coupled properties is of fundamental and technological importance1 (for example, in multiferroics2–5 or high-temperature superconductors6–9). However, determining the microscopic mechanisms responsible for the simultaneous presence of different orders is difficult, making it hard to predict material phenomenology10,11 or modify properties12–16. Here, using a Quantum Gas to engineer an adjustable interaction at the microscopic level, we demonstrate scenarios of competition, coexistence and mutual enhancement of two orders. For the enhancement scenario, the presence of one order lowers the critical point of the other. Our system is realized by a Bose–Einstein condensate that can undergo self-organization phase transitions in two optical resonators17, resulting in two distinct crystalline density orders. We characterize the coupling between these orders by measuring the composite order parameter and the elementary excitations and explain our results with a mean-field free-energy model derived from a microscopic Hamiltonian. Our system is ideally suited to explore Quantum tricritical points18 and can be extended to study the interplay of spin and density orders19 as a function of temperature20.
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monitoring and manipulating higgs and goldstone modes in a supersolid Quantum Gas
Science, 2017Co-Authors: Julian Léonard, Tobias Donner, Andrea Morales, Philip Zupancic, Tilman EsslingerAbstract:Higgs and Goldstone modes are collective excitations of the amplitude and phase of an order parameter that is related to the breaking of a continuous symmetry. We directly studied these modes in a supersolid Quantum Gas created by coupling a Bose-Einstein condensate to two optical cavities, whose field amplitudes form the real and imaginary parts of a U(1)-symmetric order parameter. Monitoring the cavity fields in real time allowed us to observe the dynamics of the associated Higgs and Goldstone modes and revealed their amplitude and phase nature. We used a spectroscopic method to measure their frequencies, and we gave a tunable mass to the Goldstone mode by exploring the crossover between continuous and discrete symmetry. Our experiments link spectroscopic measurements to the theoretical concept of Higgs and Goldstone modes.
Ryosuke Yano - One of the best experts on this subject based on the ideXlab platform.
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Fast and accurate calculation of dilute Quantum Gas using Uehling-Uhlenbeck model equation
Journal of Computational Physics, 2017Co-Authors: Ryosuke YanoAbstract:The Uehling-Uhlenbeck (U-U) model equation is studied for the fast and accurate calculation of a dilute Quantum Gas. In particular, the direct simulation Monte Carlo (DSMC) method is used to solve the U-U model equation. DSMC analysis based on the U-U model equation is expected to enable the thermalization to be accurately obtained using a small number of sample particles and the dilute Quantum Gas dynamics to be calculated in a practical time. Finally, the applicability of DSMC analysis based on the U-U model equation to the fast and accurate calculation of a dilute Quantum Gas is confirmed by calculating the viscosity coefficient of a Bose Gas on the basis of the Green-Kubo expression and the shock layer of a dilute Bose Gas around a cylinder.
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Numerical method toward fast and accurate calculation of dilute Quantum Gas using Uehling-Uhlenbeck model equation
arXiv: Computational Physics, 2015Co-Authors: Ryosuke YanoAbstract:The numerical method toward the fast and accurate calculation of the dilute Quantum Gas is studied by proposing the Uehing-Uhlenbeck (U-U) model equation. In particular, the direct simulation Monte Carlo (DSMC) method is used to solve the U-U model equation. The DSMC analysis of the U-U model equation surely enables us to obtain the accurate thermalization using a small number of sample particles and calculate the dilute Quantum Gas dynamics in practical time. Finally, the availability of the DSMC analysis of the U-U model equation toward the fast and accurate calculation of the dilute Quantum Gas is confirmed by calculating the viscosity coefficient of the Bose Gas on the basis of Green-Kubo expression or shock layer of the dilute Bose Gas around a circular cylinder
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semi classical expansion of distribution function using modified hermite polynomials for Quantum Gas
Physica A-statistical Mechanics and Its Applications, 2014Co-Authors: Ryosuke YanoAbstract:The author proposes the semi-classical expansion of the distribution function using modified Hermite polynomials to calculate moment equations for Quantum Gas. The completeness of the semi-classical expansion of the distribution function is not satisfied, whereas we can conjecture that moment equations obtained using the semi-classical expansion coincides with those obtained using Uehling–Uhlenbeck equation. Actually, Grad’s 13 moment equations, which are calculated using correct Grad’s 13 moment equation, coincide with those, which are calculated using the semi-classical expansion of the distribution function, when the collisional term of the Uehling–Uhlenbeck equation is replaced with the Quantum Bhatnagar–Gross–Krook model.
Tilman Esslinger - One of the best experts on this subject based on the ideXlab platform.
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Continuous feedback on a Quantum Gas coupled to an optical cavity
New Journal of Physics, 2020Co-Authors: Katrin Kroeger, Tobias Donner, Nishant Dogra, Rodrigo Rosa-medina, Marcin Paluch, Francesco Ferri, Tilman EsslingerAbstract:We present an active feedback scheme acting continuously on the state of a Quantum Gas dispersively coupled to a high-finesse optical cavity. The Quantum Gas is subject to a transverse pump laser field inducing a self-organization phase transition, where the Gas acquires a density modulation and photons are scattered into the resonator. Photons leaking from the cavity allow for a real-time and non-destructive readout of the system. We stabilize the mean intra-cavity photon number through a micro-processor controlled feedback architecture acting on the intensity of the transverse pump field. The feedback scheme can keep the mean intra-cavity photon number $n_\text{ph}$ constant, in a range between $n_\text{ph}=0.17\pm 0.04$ and $n_\text{ph}=27.6\pm 0.5$, and for up to 4 s. Thus we can engage the stabilization in a regime where the system is very close to criticality as well as deep in the self-organized phase. The presented scheme allows us to approach the self-organization phase transition in a highly controlled manner and is a first step on the path towards the realization of many-body phases driven by tailored feedback mechanisms.
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Coupling two order parameters in a Quantum Gas
Nature Materials, 2018Co-Authors: Andrea Morales, Tilman Esslinger, Philip Zupancic, Julian Léonard, Tobias DonnerAbstract:Ultracold atoms can model single-order Quantum phases, but coupling of different order parameters has not been shown. Here, this is demonstrated using two optical resonators, facilitating exploration of multiple-order systems such as multiferroics. Controlling matter to simultaneously support coupled properties is of fundamental and technological importance^ 1 (for example, in multiferroics^ 2 – 5 or high-temperature superconductors^ 6 – 9 ). However, determining the microscopic mechanisms responsible for the simultaneous presence of different orders is difficult, making it hard to predict material phenomenology^ 10 , 11 or modify properties^ 12 – 16 . Here, using a Quantum Gas to engineer an adjustable interaction at the microscopic level, we demonstrate scenarios of competition, coexistence and mutual enhancement of two orders. For the enhancement scenario, the presence of one order lowers the critical point of the other. Our system is realized by a Bose–Einstein condensate that can undergo self-organization phase transitions in two optical resonators^ 17 , resulting in two distinct crystalline density orders. We characterize the coupling between these orders by measuring the composite order parameter and the elementary excitations and explain our results with a mean-field free-energy model derived from a microscopic Hamiltonian. Our system is ideally suited to explore Quantum tricritical points^ 18 and can be extended to study the interplay of spin and density orders^ 19 as a function of temperature^ 20 .
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Coupling two order parameters in a Quantum Gas
Nature materials, 2018Co-Authors: Andrea Morales, Tilman Esslinger, Philip Zupancic, Julian Léonard, Tobias DonnerAbstract:Controlling matter to simultaneously support multiple coupled properties is of fundamental and technological importance. For example, the simultaneous presence of magnetic and ferroelectric orders in multiferroic materials leads to enhanced functionalities. In high-temperature superconductors, intertwining between charge- and spin-order can form superconducting states at high transition temperatures. However, pinning down the microscopic mechanisms responsible for the simultaneous presence of different orders is difficult, making it hard to predict the phenomenology of a material or to experimentally modify its properties. Here we use a Quantum Gas to engineer an adjustable interaction at the microscopic level between two orders, and demonstrate scenarios of competition, coexistence and coupling between them. In the latter case, intriguingly, the presence of one order lowers the critical point of the other. Our system is realized by a Bose-Einstein condensate which can undergo self-organization phase transitions in two optical resonators, resulting in two distinct crystalline density orders. We characterize the intertwining between these orders by measuring the composite order parameter and the elementary excitations. We explain our results with a mean-field free energy model, which is derived from a microscopic Hamiltonian. Our system is ideally suited to explore properties of Quantum tricritical points as recently realized in and can be extended to study the interplay of spin and density orders also as a function of temperature.
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coupling two order parameters in a Quantum Gas
Nature Materials, 2018Co-Authors: Andrea Morales, Tilman Esslinger, Philip Zupancic, Julian Léonard, Tobias DonnerAbstract:Controlling matter to simultaneously support coupled properties is of fundamental and technological importance1 (for example, in multiferroics2–5 or high-temperature superconductors6–9). However, determining the microscopic mechanisms responsible for the simultaneous presence of different orders is difficult, making it hard to predict material phenomenology10,11 or modify properties12–16. Here, using a Quantum Gas to engineer an adjustable interaction at the microscopic level, we demonstrate scenarios of competition, coexistence and mutual enhancement of two orders. For the enhancement scenario, the presence of one order lowers the critical point of the other. Our system is realized by a Bose–Einstein condensate that can undergo self-organization phase transitions in two optical resonators17, resulting in two distinct crystalline density orders. We characterize the coupling between these orders by measuring the composite order parameter and the elementary excitations and explain our results with a mean-field free-energy model derived from a microscopic Hamiltonian. Our system is ideally suited to explore Quantum tricritical points18 and can be extended to study the interplay of spin and density orders19 as a function of temperature20.
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monitoring and manipulating higgs and goldstone modes in a supersolid Quantum Gas
Science, 2017Co-Authors: Julian Léonard, Tobias Donner, Andrea Morales, Philip Zupancic, Tilman EsslingerAbstract:Higgs and Goldstone modes are collective excitations of the amplitude and phase of an order parameter that is related to the breaking of a continuous symmetry. We directly studied these modes in a supersolid Quantum Gas created by coupling a Bose-Einstein condensate to two optical cavities, whose field amplitudes form the real and imaginary parts of a U(1)-symmetric order parameter. Monitoring the cavity fields in real time allowed us to observe the dynamics of the associated Higgs and Goldstone modes and revealed their amplitude and phase nature. We used a spectroscopic method to measure their frequencies, and we gave a tunable mass to the Goldstone mode by exploring the crossover between continuous and discrete symmetry. Our experiments link spectroscopic measurements to the theoretical concept of Higgs and Goldstone modes.
Julian Léonard - One of the best experts on this subject based on the ideXlab platform.
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Coupling two order parameters in a Quantum Gas
Nature Materials, 2018Co-Authors: Andrea Morales, Tilman Esslinger, Philip Zupancic, Julian Léonard, Tobias DonnerAbstract:Ultracold atoms can model single-order Quantum phases, but coupling of different order parameters has not been shown. Here, this is demonstrated using two optical resonators, facilitating exploration of multiple-order systems such as multiferroics. Controlling matter to simultaneously support coupled properties is of fundamental and technological importance^ 1 (for example, in multiferroics^ 2 – 5 or high-temperature superconductors^ 6 – 9 ). However, determining the microscopic mechanisms responsible for the simultaneous presence of different orders is difficult, making it hard to predict material phenomenology^ 10 , 11 or modify properties^ 12 – 16 . Here, using a Quantum Gas to engineer an adjustable interaction at the microscopic level, we demonstrate scenarios of competition, coexistence and mutual enhancement of two orders. For the enhancement scenario, the presence of one order lowers the critical point of the other. Our system is realized by a Bose–Einstein condensate that can undergo self-organization phase transitions in two optical resonators^ 17 , resulting in two distinct crystalline density orders. We characterize the coupling between these orders by measuring the composite order parameter and the elementary excitations and explain our results with a mean-field free-energy model derived from a microscopic Hamiltonian. Our system is ideally suited to explore Quantum tricritical points^ 18 and can be extended to study the interplay of spin and density orders^ 19 as a function of temperature^ 20 .
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Coupling two order parameters in a Quantum Gas
Nature materials, 2018Co-Authors: Andrea Morales, Tilman Esslinger, Philip Zupancic, Julian Léonard, Tobias DonnerAbstract:Controlling matter to simultaneously support multiple coupled properties is of fundamental and technological importance. For example, the simultaneous presence of magnetic and ferroelectric orders in multiferroic materials leads to enhanced functionalities. In high-temperature superconductors, intertwining between charge- and spin-order can form superconducting states at high transition temperatures. However, pinning down the microscopic mechanisms responsible for the simultaneous presence of different orders is difficult, making it hard to predict the phenomenology of a material or to experimentally modify its properties. Here we use a Quantum Gas to engineer an adjustable interaction at the microscopic level between two orders, and demonstrate scenarios of competition, coexistence and coupling between them. In the latter case, intriguingly, the presence of one order lowers the critical point of the other. Our system is realized by a Bose-Einstein condensate which can undergo self-organization phase transitions in two optical resonators, resulting in two distinct crystalline density orders. We characterize the intertwining between these orders by measuring the composite order parameter and the elementary excitations. We explain our results with a mean-field free energy model, which is derived from a microscopic Hamiltonian. Our system is ideally suited to explore properties of Quantum tricritical points as recently realized in and can be extended to study the interplay of spin and density orders also as a function of temperature.
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coupling two order parameters in a Quantum Gas
Nature Materials, 2018Co-Authors: Andrea Morales, Tilman Esslinger, Philip Zupancic, Julian Léonard, Tobias DonnerAbstract:Controlling matter to simultaneously support coupled properties is of fundamental and technological importance1 (for example, in multiferroics2–5 or high-temperature superconductors6–9). However, determining the microscopic mechanisms responsible for the simultaneous presence of different orders is difficult, making it hard to predict material phenomenology10,11 or modify properties12–16. Here, using a Quantum Gas to engineer an adjustable interaction at the microscopic level, we demonstrate scenarios of competition, coexistence and mutual enhancement of two orders. For the enhancement scenario, the presence of one order lowers the critical point of the other. Our system is realized by a Bose–Einstein condensate that can undergo self-organization phase transitions in two optical resonators17, resulting in two distinct crystalline density orders. We characterize the coupling between these orders by measuring the composite order parameter and the elementary excitations and explain our results with a mean-field free-energy model derived from a microscopic Hamiltonian. Our system is ideally suited to explore Quantum tricritical points18 and can be extended to study the interplay of spin and density orders19 as a function of temperature20.
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monitoring and manipulating higgs and goldstone modes in a supersolid Quantum Gas
Science, 2017Co-Authors: Julian Léonard, Tobias Donner, Andrea Morales, Philip Zupancic, Tilman EsslingerAbstract:Higgs and Goldstone modes are collective excitations of the amplitude and phase of an order parameter that is related to the breaking of a continuous symmetry. We directly studied these modes in a supersolid Quantum Gas created by coupling a Bose-Einstein condensate to two optical cavities, whose field amplitudes form the real and imaginary parts of a U(1)-symmetric order parameter. Monitoring the cavity fields in real time allowed us to observe the dynamics of the associated Higgs and Goldstone modes and revealed their amplitude and phase nature. We used a spectroscopic method to measure their frequencies, and we gave a tunable mass to the Goldstone mode by exploring the crossover between continuous and discrete symmetry. Our experiments link spectroscopic measurements to the theoretical concept of Higgs and Goldstone modes.
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Monitoring and manipulating Higgs and Goldstone modes in a supersolid Quantum Gas
Science (New York N.Y.), 2017Co-Authors: Julian Léonard, Tobias Donner, Andrea Morales, Philip Zupancic, Tilman EsslingerAbstract:Access to collective excitations lies at the heart of our understanding of Quantum many-body systems. We study the Higgs and Goldstone modes in a supersolid Quantum Gas that is created by coupling a Bose-Einstein condensate symmetrically to two optical cavities. The cavity fields form a U(1)-symmetric order parameter that can be modulated and monitored along both quadratures in real time. This enables us to measure the excitation energies across the superfluid-supersolid phase transition, establish their amplitude and phase nature, as well as characterize their dynamics from an impulse response. Furthermore, we can give a tunable mass to the Goldstone mode at the crossover between continuous and discrete symmetry by changing the coupling of the Quantum Gas with either cavity.
Yvan Castin - One of the best experts on this subject based on the ideXlab platform.
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exact scaling transform for a unitary Quantum Gas in a time dependent harmonic potential
Comptes Rendus Physique, 2004Co-Authors: Yvan CastinAbstract:Abstract A unitary Quantum Gas is a Gas of Quantum particles with a binary interaction of infinite scattering length and negligible range. It has been produced in recent experiments with Gases of fermionic atoms by means of a Feshbach resonance. Using the Fermi pseudo-potential model for the atomic interaction, we show that the time evolution of such a Gas in an isotropic three-dimensional time dependent harmonic trap is exactly given by a gauge and scaling transform. To cite this article: Y. Castin, C. R. Physique 5 (2004).
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Exact scaling transform for a unitary Quantum Gas in a time dependent harmonic potential
Comptes Rendus Physique, 2004Co-Authors: Yvan CastinAbstract:A unitary Quantum Gas is a Gas of Quantum particles with a binary interaction of infinite scattering length and negligible range. It has been produced in recent experiments with Gases of fermionic atoms by means of a Feshbach resonance. Using the Fermi pseudo-potential model for the atomic interaction, we show that the time evolution of such a Gas in an isotropic three-dimensional time dependent harmonic trap is exactly given by a gauge and scaling transform.
