| 1. |
- Di Stefano, Omar, et al.
(författare)
-
Interaction of Mechanical Oscillators Mediated by the Exchange of Virtual Photon Pairs
- 2019
-
Ingår i: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 122:3
-
Tidskriftsartikel (refereegranskat)abstract
- Two close parallel mirrors attract due to a small force (Casimir effect) originating from the quantum vacuum fluctuations of the electromagnetic field. These vacuum fluctuations can also induce motional forces exerted upon one mirror when the other one moves. Here, we consider an optomechanical system consisting of two vibrating mirrors constituting an optical resonator. We find that motional forces can determine noticeable coupling rates between the two spatially separated vibrating mirrors. We show that, by tuning the two mechanical oscillators into resonance, energy is exchanged between them at the quantum level. This coherent motional coupling is enabled by the exchange of virtual photon pairs, originating from the dynamical Casimir effect. The process proposed here shows that the electromagnetic quantum vacuum is able to transfer mechanical energy somewhat like an ordinary fluid. We show that this system can also operate as a mechanical parametric down-converter even at very weak excitations. These results demonstrate that vacuum-induced motional forces open up new possibilities for the development of optomechanical quantum technologies.
|
|
| 2. |
- MacRí, Vincenzo, et al.
(författare)
-
Revealing higher-order light and matter energy exchanges using quantum trajectories in ultrastrong coupling
- 2022
-
Ingår i: Physical Review A. - 2469-9934 .- 2469-9926. ; 105:2
-
Tidskriftsartikel (refereegranskat)abstract
- The dynamics of open quantum systems is often modeled using master equations, which describe the expected outcome of an experiment (i.e., the average over many realizations of the same dynamics). Quantum trajectories, instead, model the outcome of ideal single experiments - the "clicks"of a perfect detector due to, e.g., spontaneous emission. The correct description of quantum jumps, which are related to random events characterizing a sudden change in the wave function of an open quantum system, is pivotal to the definition of quantum trajectories. In this article, we extend the formalism of quantum trajectories to open quantum systems with ultrastrong coupling (USC) between light and matter by properly defining jump operators in this regime. In such systems, exotic higher-order quantum-state and energy transfer can take place without conserving the total number of excitations in the system. The emitted field of such USC systems bears signatures of these higher-order processes, and significantly differs from similar processes at lower coupling strengths. Notably, the emission statistics must be taken at a single quantum trajectory level, since the signatures of these processes are washed out by the "averaging"of a master equation. We analyze the impact of the chosen unraveling (i.e., how one collects the output field of the system) for the quantum trajectories and show that these effects of the higher-order USC processes can be revealed in experiments by constructing histograms of detected quantum jumps. We illustrate these ideas by analyzing the excitation of two atoms by a single photon [Garziano, Phys. Rev. Lett. 117, 043601 (2016)0031-900710.1103/PhysRevLett.117.043601]. For example, quantum trajectories reveal that keeping track of the quantum jumps from the atoms allows one to reconstruct both the oscillations between one photon and two atoms as well as emerging Rabi oscillations between the two atoms.
|
|
| 3. |
- MacRí, Vincenzo, et al.
(författare)
-
Simple preparation of Bell and Greenberger-Horne-Zeilinger states using ultrastrong-coupling circuit QED
- 2018
-
Ingår i: Physical Review A. - 2469-9934 .- 2469-9926. ; 98:6
-
Tidskriftsartikel (refereegranskat)abstract
- The ability to entangle quantum systems is crucial for many applications in quantum technology, including quantum communication and quantum computing. Here, we propose a simple and versatile setup for deterministically creating Bell and Greenberger-Horne-Zeilinger states between photons of different frequencies in a two-step protocol. The setup consists of a quantum bit (qubit) coupled ultrastrongly to three photonic resonator modes. The only operations needed in our protocol are to put the qubit in a superposition state and then tune its frequency in and out of resonance with sums of the resonator-mode frequencies. By choosing which frequency we tune the qubit to, we select which entangled state we create. We show that our protocol can be implemented with high fidelity using feasible experimental parameters in state-of-the-art circuit quantum electrodynamics. One possible application of our setup is as a node distributing entanglement in a quantum network.
|
|
| 4. |
- Settineri, Alessio, et al.
(författare)
-
Dissipation and thermal noise in hybrid quantum systems in the ultrastrong-coupling regime
- 2018
-
Ingår i: Physical Review A. - 2469-9934 .- 2469-9926. ; 98:5
-
Tidskriftsartikel (refereegranskat)abstract
- The interaction among the components of a hybrid quantum system is often neglected when considering the coupling of these components to an environment. However, if the interaction strength is large, this approximation leads to unphysical predictions, as has been shown for cavity-QED and optomechanical systems in the ultrastrong-coupling regime. To deal with these cases, master equations with dissipators retaining the interaction between these components have been derived for the quantum Rabi model and for the standard optomechanical Hamiltonian. In this article, we go beyond these previous derivations and present a general master equation approach for arbitrary hybrid quantum systems interacting with thermal reservoirs. Specifically, our approach can be applied to describe the dynamics of open hybrid systems with harmonic, quasiharmonic, and anharmonic transitions. We apply our approach to study the influence of temperature on multiphoton vacuum Rabi oscillations in circuit QED. We also analyze the influence of temperature on the conversion of mechanical energy into photon pairs in an optomechanical system, which has been recently described at zero temperature. We compare our results with previous approaches, finding that these sometimes overestimate decoherence rates and underestimate excited-state populations.
|
|
