The observation of single-photon optomechanical effects is a desired task in cavity optomechanics. However, the realization of ultrastrong optomechanical interaction remains a big challenge. Here we present an all-optical scheme to simulate ultrastrong optomechanical coupling based on a Fredkin-type interaction, which consists of two exchange-coupled modes with the coupling strength depending on the photon number in another controller mode. This coupling enhancement is assisted by the displacement amplification according to the physical idea of the Bogoliubov approximation, which is realized by utilizing a strong driving to pump one of the two exchanging modes. Our numerical simulations demonstrate that the enhanced optomechanical coupling can enter the single-photon strong-coupling and even ultrastrong-coupling regimes. We also show the creation of macroscopic quantum superposed states and the implementation of a weak-to-strong transition for quantum measurement in this system. This work will pave the way to quantum simulation of single-photon optomechanical effects with current experimental platforms.
The observation of single-photon optomechanical effects is a desired task in cavity optomechanics. However, the realization of ultrastrong optomechanical interaction remains a big challenge. Here we present an all-optical scheme to simulate ultrastrong optomechanical coupling based on a Fredkin-type interaction, which consists of two exchange-coupled modes with the coupling strength depending on the photon number in another controller mode. This coupling enhancement is assisted by the displacement amplification according to the physical idea of the Bogoliubov approximation, which is realized by utilizing a strong driving to pump one of the two exchanging modes. Our numerical simulations demonstrate that the enhanced optomechanical coupling can enter the single-photon strong-coupling and even ultrastrong-coupling regimes. We also show the creation of macroscopic quantum superposed states and the implementation of a weak-to-strong transition for quantum measurement in this system. This work will pave the way to quantum simulation of single-photon optomechanical effects with current experimental platforms.
The realization of multimode optomechanical interactions in the single-photon strong-coupling regime is a desired task in cavity optomechanics, but it remains a big challenge in realistic physical systems. In this work we propose a reliable scheme to simulate a three-mode optomechanical system working in the single-photon strong-coupling regime based on the Fredkin-type interaction. This is achieved by utilizing two strong drivings to the two exchange-coupled modes in the Fredkin-type coupling involving one optical mode and two mechanical-like modes. As an application of this enhanced three-mode nonlinear optomechanical coupling, we show how to generate entangled cat states of the mechanical-like modes using the conditional displacement mechanism. The quantum coherence effects in the generated states are investigated by calculating the two-mode joint Wigner function and quantum entanglement. The influence of the system dissipation on the state generation is also considered. This work will open up a different route to the study of multimode optomechanical interactions at the single-photon level.
Ultrastrong optomechanical interaction is a significant element for the study of the fundamentals and applications of optomechanical physics, but its realization remains a big challenge in the field of optomechanics. In this work, we propose a reliable scheme to realize a generalized ultrastrong optomechanical-like coupling in a cross-Kerr-type coupled two-bosonic-mode system, in which one of the two bosonic modes is strongly driven. The generalized optomechanical-like interaction takes the form of a product of the excitation number operator of one mode and the rotated quadrature operator of the other mode. Here, both the coupling strength and the phase angle of the rotated quadrature operator are tunable via the driving field. The optomechanical-like coupling can be strongly enhanced to enter the ultrastrong-coupling regime, where the few-photon optomechanical effects such as photon blockade and macroscopic quantum superposition become accessible. The controllability of the quadrature phase angle provides a new degree of freedom for the manipulation of optomechanical systems and enables the implementation of geometric quantum operations. We also present some discussions on the experimental implementation of this scheme. This study will pave the way to the study of quantum physics and quantum technology at the few-photon level in optomechanical systems.
We propose a reliable scheme to simulate tunable and ultrastrong mixed (first-order and quadratic optomechanical couplings coexisting) optomechanical interactions in a coupled two-mode bosonic system, in which the two modes are coupled by a cross-Kerr interaction and one of the two modes is driven through both the single- and two-excitation processes. We show that the mixed-optomechanical interactions can enter the single-photon strong-coupling and even ultrastrong-coupling regimes. The strengths of both the first-order and quadratic optomechanical couplings can be controlled on demand, and hence first-order, quadratic, and mixed optomechanical models can be realized. In particular, the thermal noise of the driven mode can be suppressed totally by introducing a proper squeezed vacuum bath. We also study how to generate the superposition of coherent squeezed state and vacuum state based on the simulated interactions. The quantum coherence effect in the generated states is characterized by calculating the Wigner function in both the closed- and open-system cases. This work will pave the way to the observation and application of ultrastrong optomechanical effects in quantum simulators.
In this thesis, I studied two different approaches which are promising for creating macroscopic quantum superpositions. The first approach, which is the main focus of this thesis, is based on optomechanical systems. The basic challenge to realize quantum effects in optomechanical systems, is considered to be the weak optomechanical coupling rate compared to the decoherence rates of the system caused by the cavity and mechanical damping. To enhance the optomechanical coupling it has been suggested to pump the cavity with coherent laser light \cite{Vitali07}. By this method the strong coupling regime in which the optomechanical coupling rate exceeds all decoherence rates has been demonstrated very recently \cite{Verhagen12,Groblacher09}. It is also known that the optomechanical systems may exhibit nonlinear behaviours such as bistability. After introducing the basic ideas of optomechanical systems in chapter 1, in chapter 2 we studied the connection between optomechanical entanglement and bistability. In chapter 3, we studied the drawback of using a laser to enhance the interaction. We studied the effect of the laser phase noise, as an additional decoherence channel, on the optomechanical entanglement. We have shown that the system is very sensitive to this new source of decoherence and the sensitivity is maximum in the bistable threshold. We discussed that our results are independent of how we model the laser phase noise. In chapter 4, we studied single photon optomechanics. In this regime, we proposed a new scheme to enhance the optomechanical coupling based on post selection. Our scheme is potentially promising to create a superposition of the massive oscillator in different motional states. We also discussed the potential application of our scheme to test some decoherence models. The second approach that we consider in this thesis is based on amplifying single photons with high gain to create micro-macro superpositions . In chapter 5, we discussed the De Martini scheme. We then present our scheme for creating optical micro-macro superposition and discussed its experimental realization under realistic conditions when losses are taken into account.
The interaction of light and matter at the single-photon level is of central importance in various fields of physics, including, e.g., condensed matter physics, astronomy, quantum optics, and quantum information. Amplification of such quantum light–matter interaction can be highly beneficial to, e.g., improve device performance, explore novel phenomena, and understand fundamental physics, and has therefore been a long-standing goal. Furthermore, simulation of light–matter interaction in the regime of ultrastrong coupling, where the interaction strength is comparable to the bare frequencies of the uncoupled systems, has also become a hot research topic, and considerable progress has been made both theoretically and experimentally in the past decade. In this review, we provide a detailed introduction of recent advances in amplification of quantum light–matter interaction and simulation of ultrastrong light–matter interaction, particularly in cavity and circuit quantum electrodynamics and in cavity optomechanics.
Cavity optomechanics represents a flexible platform for the implementation of quantum technologies, useful in particular for the realization of quantum interfaces, quantum sensors and quantum information processing. However, the dispersive, radiation-pressure interaction between the mechanical and the electromagnetic modes is typically very weak, harnessing up to now the demonstration of interesting nonlinear dynamics and quantum control at the single photon level. It has already been shown both theoretically and experimentally that if the interaction is mediated by a Josephson circuit, one can have an effective dynamics corresponding to a huge enhancement of the single-photon optomechanical coupling. Here we analyze in detail this phenomenon in the general case when the cavity mode and the mechanical mode interact via an off-resonant qubit. Using a Schrieffer-Wolff approximation treatment, we determine the regime where this tripartite hybrid system behaves as an effective cavity optomechanical system in the strong coupling regime.