Towards Quantum Entanglement in Nanoelectromechanical Devices (original) (raw)
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Towards mechanical entanglement in nano-electromechanical devices
2003
We study arrays of mechanical oscillators in the quantum domain and demonstrate how the motions of distant oscillators can be entangled without the need for control of individual oscillators and without a direct interaction between them. These oscillators are thought of as being members of an array of nano-electromechanical resonators with a voltage being applicable between neighboring resonators. Sudden non-adiabatic switching of the interaction results in a squeezing of the states of the mechanical oscillators, leading to an entanglement transport in chains of mechanical oscillators. We discuss spatial dimensions, Q-factors, temperatures and decoherence sources in some detail, and find a distinct robustness of the entanglement in the canonical coordinates in such a scheme. We also briefly discuss the challenging aspect of detection of the generated entanglement.
Entanglement between distant macroscopic mechanical and spin systems
Nature Physics, 2020
Entanglement is a vital property of multipartite quantum systems, characterised by the inseparability of quantum states of objects regardless of their spatial separation. Generation of entanglement between increasingly macroscopic and disparate systems is an ongoing effort in quantum science which enables hybrid quantum networks [1, 2], quantum-enhanced sensing [3], and probing the fundamental limits of quantum theory [4, 5]. The disparity of hybrid systems and the vulnerability of quantum correlations have thus far hampered the generation of macroscopic hybrid entanglement. Here we demonstrate, for the first time, generation of an entangled state between the motion of a macroscopic mechanical oscillator and a collective atomic spin oscillator, as witnessed by an Einstein-Podolsky-Rosen variance below the separability limit [6], 0.83 ± 0.02 < 1. The mechanical oscillator is a millimeter-size dielectric membrane [7] and the spin oscillator is an ensemble of 10 9 atoms in a magnetic field [8]. Light propagating through the two spatially separated systems generates entanglement due to the collective spin playing the role of an effective negative-mass reference frame [9-12] and providing, under ideal circumstances, a backaction-free subspace [13]; in the experiment, quantum backaction is suppressed by 4.6 dB. Our results pave the road towards measurement of motion beyond the standard quantum limits of sensitivity with applications in force, acceleration, and gravitational wave detection [14, 15], as well as towards teleportation-based protocols [16] in hybrid quantum networks.
Stationary entanglement between macroscopic mechanical oscillators
The European Physical Journal D, 2003
We show that the optomechanical coupling between an optical cavity mode and the two movable cavity mirrors is able to entangle two different macroscopic oscillation modes of the mirrors. This continuous variable entanglement is maintained by the light bouncing between the mirrors and is robust against thermal noise. In fact, it could be experimentally demonstrated using present technology.
Entangled-state generation and Bell inequality violations in nanomechanical resonators
We investigate theoretically the conditions under which a multi-mode nanomechanical resonator, operated as a purely mechanical parametric oscillator, can be driven into highly nonclassical states. We find that when the device can be cooled to near its ground state, and certain mode matching conditions are satisfied, it is possible to prepare distinct resonator modes in quantum entangled states that violate Bell inequalities with homodyne quadrature measurements. We analyze the parameter regimes for such Bell inequality violations, and while experimentally challenging, we believe that the realization of such states lies within reach. This is a re-imagining of a quintessential quantum optics experiment by using phonons that represent tangible mechanical vibrations.
Quantum entanglement of nanocantilevers
Physical Review A, 2010
We propose a scheme to entangle two mechanical nanocantilevers through indirect interactions mediated by a gas of ultra cold atoms. We envisage a system of nanocantilevers magnetically coupled to a Bose-Einstein condensate of atoms and focus on studying the dark states of the system. These dark states are entangled states of the two nanocantilevers, with no coupling to the atomic condensate. In the absence of dissipation, the degree of entanglement is found to oscillate with time, while if dissipation is included the system is found to relax to a time-independent statistical mixture of dark states. This opens up the possibility of achieving long-lived entangled nanocantilever states.
Creation and localization of entanglement in a simple configuration of coupled harmonic oscillators
We investigate a simple arrangement of coupled harmonic oscillators which brings out some interesting effects concerning creation of entanglement. It is well known that if each member in a linear chain of coupled harmonic oscillators is prepared in a " classical state, " such as a pure coherent state or a mixed thermal state, no entanglement is created in the rotating wave approximation. On the other hand, if one of the oscillators is prepared in a nonclassical state pure squeezed state, for instance, entanglement may be created between members of the chain. In the setup considered here, we found that a great family of nonclassical squeezed states can localize entanglement in such a way that distant oscillators never become entangled. We present a detailed study of this particular localization phenomenon. Our results may find application in future solid state implementations of quantum computers, and we suggest an electromechanical system consisting of an array of coupled micromechanical oscillators as a possible implementation.
Physical Review A, 2013
In this paper, we propose a scheme for generating steady-state entanglement of remote micromechanical oscillators in unidirectionally-coupled cavities. For the system of two mechanical oscillators, we show that when two cavity modes in each cavity are driven at red-and blue-detuned sidebands, respectively, a stationary two-mode squeezed vacuum state of the two mechanical oscillators can be generated with the help of the cavity dissipation. The degree of squeezing is controllable by adjusting the relative strength of the pump lasers. Our calculations also show that the achieved mechanical entanglement is robust against thermal fluctuations of phononic environments. For the case of multiple mechanical oscillators, we find that the steady-state genuine multipartite entanglement can also be built up among the remote mechanical oscillators by the cavity dissipation. The present scheme does not require nonclassical light input or conditional quantum measurements, and it can be realized with current experimental technology.
We propose a method to generate stationary entanglement between two macroscopic vibrating elements (micro-mechanical resonators (MRs)), via a transmission line resonator (TLR) field mode, where the MRs are coupled to the TLR capacitively. In this paper two situations are studied; (i) a driving on TLR field with an external microwave pulse, (ii) driving on TLR field and simultaneous driving on two MRs. Here, the entanglement is quantified by the logarithmic negativity. As our proposed system is a continuous variable system, the logarithmic negativity is defined in terms of covariance matrix. We have shown that the second case leads to much stronger entanglement, even at a few milli Kelvin temperatures.
Quantum entanglement between a nonlinear nanomechanical resonator and a microwave field
Physical Review E, 2011
We consider a theoretical model for a nonlinear nanomechanical resonator coupled to a superconducting microwave resonator. The nanomechanical resonator is driven parametrically at twice its resonance frequency, while the superconducting microwave resonator is driven with two tones that differ in frequency by an amount equal to the parametric driving frequency. We show that the semi-classical approximation of this system has an interesting fixed point bifurcation structure. In the semi-classical dynamics a transition from stable fixed points to limit cycles is observed as one moves from positive to negative detuning. We show that signatures of this bifurcation structure are also present in the full dissipative quantum system and further show that it leads to mixed state entanglement between the nanomechanical resonator and the microwave cavity in the dissipative quantum system that is a maximum close to the semi-classical bifurcation. Quantum signatures of the semi-classical limit-cycles are presented.
Quantum Information Processing, 2021
We systematically study the influence of simultaneously modulating the input laser intensity and quantum dot (QD) resonance frequecy on the mean-field dynamics, fluctuation energy transfer and entanglement in a optomechanical semiconductor resonator embedded with a QD. We show that the modulation and the hybrid system can be engineered to attain the desired mean-field values, control the fluctuation energy transfer and the entanglement between the various degrees of freedom. A remarkably high degree of entanglement can be achieved by modulating only the QD frequency. The interplay between the two modulations leads to an entanglement which lies between that generated solely by modulating either the QD or the pump laser intensity. A transition from low stationary to large dynamical entanglement occurs as we switch on the modulation. This study opens up new possibilities for optimal control strategies and can be used for data signal transfer and storage in quantum communication platforms.