Nima Nooshi

Bio: Nima Nooshi is an academic researcher from Max Planck Society. The author has contributed to research in topics: Oscillation & Radiation pressure. The author has an hindex of 5, co-authored 10 publications receiving 1489 citations.

Theory of ground state cooling of a mechanical oscillator using dynamical backaction.

Abstract: A quantum theory of cooling of a mechanical oscillator by radiation pressure-induced dynamical backaction is developed, which is analogous to sideband cooling of trapped ions. We find that final occupancies well below unity can be attained when the mechanical oscillation frequency is larger than the optical cavity linewidth. It is shown that the final average occupancy can be retrieved directly from the optical output spectrum.

Radiation pressure cooling of a micromechanical oscillator using dynamical backaction.

Abstract: Cooling of a 58 MHz micromechanical resonator from room temperature to 11 K is demonstrated using cavity enhanced radiation pressure. Detuned pumping of an optical resonance allows enhancement of the blueshifted motional sideband (caused by the oscillator's Brownian motion) with respect to the redshifted sideband leading to cooling of the mechanical oscillator mode. The reported cooling mechanism is a manifestation of the effect of radiation pressure induced dynamical backaction. These results constitute an important step towards achieving ground state cooling of a mechanical oscillator.

Cavity-assisted backaction cooling of mechanical resonators

Abstract: We analyze the quantum regime of the dynamical backaction cooling of a mechanical resonator assisted by a driven harmonic oscillator (cavity). Our treatment applies to both optomechanical and electromechanical realizations and includes the effect of thermal noise in the driven oscillator. In the perturbative case, we derive the corresponding motional master equation using the Nakajima-Zwanzig formalism and calculate the corresponding output spectrum for the optomechanical case. Then we analyze the strong optomechanical coupling regime in the limit of small cavity linewidth. Finally, we consider the steady state covariance matrix of the two coupled oscillators for arbitrary input power and obtain an analytical expression for the final mechanical occupancy. This is used to optimize the drive's detuning and input power for an experimentally relevant range of parameters that includes the resolved-sideband-limit ground state cooling regime.

Cavity-Assisted Back Action Cooling of Mechanical Resonators

Abstract: We analyze the quantum regime of the dynamical backaction cooling of a mechanical resonator assisted by a driven harmonic oscillator (cavity). Our treatment applies to both optomechanical and electromechanical realizations and includes the effect of thermal noise in the driven oscillator. In the perturbative case, we derive the corresponding motional master equation using the Nakajima-Zwanzig formalism and calculate the corresponding output spectrum for the optomechanical case. Then we analyze the strong optomechanical coupling regime in the limit of small cavity linewidth. Finally we consider the steady state covariance matrix of the two coupled oscillators for arbitrary input power and obtain an analytical expression for the final mechanical occupancy. This is used to optimize the drive's detuning and input power for an experimentally relevant range of parameters that includes the "ground state cooling" regime.

Radiation Pressure Cooling of a Micromechanical Oscillator Using Dynamical Backaction

Abstract: In this paper, the authors report on the first the experimental observation of this phenomenon using very high-finesse toroidal silica microresonators (Schliesser, 2006). These structures possess whispering gallery type optical modes (with photon lifetimes up to 500 ns) while simultaneously exhibiting micromechanical resonances in the radio-frequency domain. We study the interaction of the intracavity light with the ~60 MHz radial breathing mode of the cavity.

Cavity Optomechanics

Abstract: We review the field of cavity optomechanics, which explores the interaction between electromagnetic radiation and nano- or micromechanical motion This review covers the basics of optical cavities and mechanical resonators, their mutual optomechanical interaction mediated by the radiation pressure force, the large variety of experimental systems which exhibit this interaction, optical measurements of mechanical motion, dynamical backaction amplification and cooling, nonlinear dynamics, multimode optomechanics, and proposals for future cavity quantum optomechanics experiments In addition, we describe the perspectives for fundamental quantum physics and for possible applications of optomechanical devices

Laser cooling of a nanomechanical oscillator into its quantum ground state

Abstract: The simple mechanical oscillator, canonically consisting of a coupled mass–spring system, is used in a wide variety of sensitive measurements, including the detection of weak forces and small masses. On the one hand, a classical oscillator has a well-defined amplitude of motion; a quantum oscillator, on the other hand, has a lowest-energy state, or ground state, with a finite-amplitude uncertainty corresponding to zero-point motion. On the macroscopic scale of our everyday experience, owing to interactions with its highly fluctuating thermal environment a mechanical oscillator is filled with many energy quanta and its quantum nature is all but hidden. Recently, in experiments performed at temperatures of a few hundredths of a kelvin, engineered nanomechanical resonators coupled to electrical circuits have been measured to be oscillating in their quantum ground state. These experiments, in addition to providing a glimpse into the underlying quantum behaviour of mesoscopic systems consisting of billions of atoms, represent the initial steps towards the use of mechanical devices as tools for quantum metrology or as a means of coupling hybrid quantum systems. Here we report the development of a coupled, nanoscale optical and mechanical resonator formed in a silicon microchip, in which radiation pressure from a laser is used to cool the mechanical motion down to its quantum ground state (reaching an average phonon occupancy number of 0.85±0.08). This cooling is realized at an environmental temperature of 20 K, roughly one thousand times larger than in previous experiments and paves the way for optical control of mesoscale mechanical oscillators in the quantum regime.

Quantum ground state and single-phonon control of a mechanical resonator

Abstract: Quantum mechanics provides a highly accurate description of a wide variety of physical systems. However, a demonstration that quantum mechanics applies equally to macroscopic mechanical systems has been a long-standing challenge, hindered by the difficulty of cooling a mechanical mode to its quantum ground state. The temperatures required are typically far below those attainable with standard cryogenic methods, so significant effort has been devoted to developing alternative cooling techniques. Once in the ground state, quantum-limited measurements must then be demonstrated. Here, using conventional cryogenic refrigeration, we show that we can cool a mechanical mode to its quantum ground state by using a microwave-frequency mechanical oscillator—a ‘quantum drum’—coupled to a quantum bit, which is used to measure the quantum state of the resonator. We further show that we can controllably create single quantum excitations (phonons) in the resonator, thus taking the first steps to complete quantum control of a mechanical system. The bizarre, often counter-intuitive predictions of quantum mechanics have been observed in atomic-scale optical and electrical systems, but efforts to demonstrate that quantum mechanics applies equally to a mechanical system, especially one large enough to be seen with the naked eye, have proved challenging. The difficulty is cooling a mechanical system to its quantum ground state, where all classical noise is eliminated. A team at the Department of Physics at the University of California, Santa Barbara, has overcome this obstacle. Using conventional cryogenic refrigeration, they cool a mechanical resonator with a very high oscillation frequency to one-fortieth of a degree above absolute zero. This resonator, called a 'quantum drum', is coupled to a superconducting quantum bit that acts as a quantum thermometer to detect whether there are any excitations left in the resonator. When it is confirmed there are none, it is further shown that a single quantum of excitation, a phonon, can be introduced in this system and exchanged between resonator and qubit many times, thereby taking the first steps towards complete quantum control of a mechanical system. Quantum mechanics provides an accurate description of a wide variety of physical systems but it is very challenging to prove that it also applies to macroscopic (classical) mechanical systems. This is because it has been impossible to cool a mechanical mode to its quantum ground state, in which all classical noise is eliminated. Recently, various mechanical devices have been cooled to a near-ground state, but this paper demonstrates the milestone result of a piezoelectric resonator with a mechanical mode cooled to its quantum ground state.

Cavity Optomechanics: Back-Action at the Mesoscale

Abstract: The coupling of optical and mechanical degrees of freedom is the underlying principle of many techniques to measure mechanical displacement, from macroscale gravitational wave detectors to microscale cantilevers used in scanning probe microscopy. Recent experiments have reached a regime where the back-action of photons caused by radiation pressure can influence the optomechanical dynamics, giving rise to a host of long-anticipated phenomena. Here we review these developments and discuss the opportunities for innovative technology as well as for fundamental science.

Sideband cooling of micromechanical motion to the quantum ground state

Abstract: It has been a long-standing goal in the field of cavity optomechanics to cool down a mechanical resonator to its motional quantum ground state by using light. Teufel et al. have now achieved just that with a recently developed system in which a drum-like flexible aluminium membrane is incorporated in a superconducting circuit. Ground-state cooling of a mechanical resonator was demonstrated for the first time last year in a different type of device, but the quantum states in this new device should be much longer lived, allowing direct tests of fundamental principles of quantum mechanics. As a first step, the authors perform a quantum-limited position measurement that is only a factor of about five away from the Heisenberg limit. The advent of laser cooling techniques revolutionized the study of many atomic-scale systems, fuelling progress towards quantum computing with trapped ions1 and generating new states of matter with Bose–Einstein condensates2. Analogous cooling techniques3,4 can provide a general and flexible method of preparing macroscopic objects in their motional ground state. Cavity optomechanical or electromechanical systems achieve sideband cooling through the strong interaction between light and motion5,6,7,8,9,10,11,12,13,14,15. However, entering the quantum regime—in which a system has less than a single quantum of motion—has been difficult because sideband cooling has not sufficiently overwhelmed the coupling of low-frequency mechanical systems to their hot environments. Here we demonstrate sideband cooling of an approximately 10-MHz micromechanical oscillator to the quantum ground state. This achievement required a large electromechanical interaction, which was obtained by embedding a micromechanical membrane into a superconducting microwave resonant circuit. To verify the cooling of the membrane motion to a phonon occupation of 0.34 ± 0.05 phonons, we perform a near-Heisenberg-limited position measurement3 within (5.1 ± 0.4)h/2π, where h is Planck’s constant. Furthermore, our device exhibits strong coupling, allowing coherent exchange of microwave photons and mechanical phonons16. Simultaneously achieving strong coupling, ground state preparation and efficient measurement sets the stage for rapid advances in the control and detection of non-classical states of motion17,18, possibly even testing quantum theory itself in the unexplored region of larger size and mass19. Because mechanical oscillators can couple to light of any frequency, they could also serve as a unique intermediary for transferring quantum information between microwave and optical domains20.