15 research outputs found
Brillouin cavity optomechanics: Single-quantum-level operations towards quantum memory applications
Cavity-enhanced Brillouin scattering interactions with gigahertz-frequency acoustic phonons offer a promising pathway towards the quantum coherent control of mechanical oscillators. In this thesis, I experimentally investigate single-quantum-level operations applied to thermal me- chanical oscillators by combining optical measurement techniques with Brillouin interactions in crystalline whispering-gallery-mode microresonator devices. These operations are explored for applications in quantum state engineering and optical quantum memories. Generating and characterising non-classical states of mechanical motion currently represents a key challenge in quantum cavity optomechanics, and the realisation of a quantum memory would enable the development of many quantum technologies. The advances reported here contribute to both of these active areas of research.
In a series of three experiments, single- and multi-phonon addition and subtraction opera- tions applied to thermal mechanical states are explored. I present the first experimental inves- tigation of single-phonon addition and subtraction operations using a joint click-dyne detection scheme, where the effect of such operations are verified by observing a characteristic doubling of the mean occupation of the state. These techniques are then extended to multi-phonon subtraction. Here, the -parameterised Wigner function of the resulting non-Gaussian states are determined, advancing the state-of-the-art for optics-based mechanical state tomography. Finally, an interferometric detection scheme is employed that implements a superposition of phonon subtractions in two time bins, and the phase coherence between these two operations is demonstrated and studied. In this thesis, I also theoretically investigate the prospects of an optical quantum memory based on Brillouin cavity optomechanics. Using realistic parameters, I show that efficient storage and retrieval of single photons is feasible, and I identify two key applications: temporal multiplexing and temporal mode manipulation. The deleterious effect of thermal noise in such optomechanical quantum light storage is also considered. To conclude, an outlook towards some near-term and long-term experimental goals that can build upon on the achievements reported is presented.Open Acces
Hybrid photon-phonon blockade
We describe a novel type of blockade in a hybrid mode generated by linear
coupling of photonic and phononic modes. We refer to this effect as hybrid
photon-phonon blockade and show how it can be generated and detected in a
driven nonlinear optomechanical superconducting system. Thus, we study
boson-number correlations in the photon, phonon, and hybrid modes in linearly
coupled microwave and mechanical resonators with a superconducting qubit
inserted in one of them. We find such system parameters for which we observe
eight types of different combinations of either blockade or tunnelling effects
(defined via the sub- and super-Poissonian statistics) for photons, phonons,
and hybrid bosons. In particular, we find that the hybrid photon-phonon
blockade can be generated by mixing the photonic and phononic modes which do
not exhibit blockade.Comment: 20 pages, 14 figure
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Dynamic Acoustic Control of Semiconductor Quantum Dot-Based Devices for Quantum Light Generation
This thesis presents work on a series of devices for the generation of photonic quantum states based on self-assembled InAs quantum dots, which are among the most technologically mature candidates for practical quantum photonic applications due to their high internal quantum efficiency, narrow linewidth, tunability and straightforward integration with photonic and electric components. The primary results presented concern sources of multi-photon entangled states and single-photon sources with high repetition rate, both of which are crucial components for emerging photonic quantum technologies. First, we propose a scheme for the sequential generation of entangled photon chains by resonant scattering of a laser field on a single charged particle in a cavity-enhanced quantum dot. The charge has an associated spin that can determine the time bin of a photon, allowing for information encoding in this degree of freedom. We demonstrate coherent operations on this spin and realize a proof-of-principle experiment of the proposed scheme by showing that the time bin of a single-photon is dependent on the measured state of the trapped spin.
The second main avenue of work investigates the effects of a surface acoustic wave, a mechanical displacement wave confined to the surface of a substrate, on the optical properties of quantum dots. In particular, we exploit the dynamic acoustically-induced tuning of the emission energy to modulate the Purcell effect in a pillar microcavity. Under resonant optical excitation we demonstrate the conversion of the continuous wave laser into a pulsed single-photon stream inheriting the acoustic frequency of 1 GHz as the repetition rate. High resolution spectroscopy reveals the presence of narrow sidebands in the emission spectrum, whose relative intensity can be controlled by the acoustic power and laser detuning. Furthermore, we develop a platform for analogous in-plane experiments by transferring GaAs membranes hosting quantum dots onto LiNbO3 substrates and patterning them into whispering gallery mode optical resonators. In addition to Purcell enhancement and acoustic tuning of the emission, the devices exhibit strong localized mechanical resonances. Finally, we perform initial experiments on the effects of a surface acoustic wave on the spin of a charge trapped in a quantum dot. We integrate acoustic transducers with charge-tunable diodes, where the charge state of the dot can be precisely controlled by an applied bias voltage, and demonstrate the frustration of optical spin pumping by the acoustic wave.This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 642688
Tunable phonon blockade in weakly nonlinear coupled mechanical resonators via Coulomb interaction
Realizing quantum mechanical behavior in micro- and nanomechanical resonators
has attracted continuous research effort. One of the ways for observing quantum
nature of mechanical objects is via the mechanism of phonon blockade. Here, we
show that phonon blockade could be achieved in a system of two weakly nonlinear
mechanical resonators coupled by a Coulomb interaction. The optimal blockade
arises as a result of the destructive quantum interference between paths
leading to two-phonon excitation. It is observed that, in comparison to a
single drive applied on one mechanical resonator, driving both the resonators
can be beneficial in many aspects; such as, in terms of the temperature
sensitivity of phonon blockade and also with regard to the tunability, by
controlling the amplitude and the phase of the second drive externally. We also
show that via a radiation pressure induced coupling in an optomechanical
cavity, phonon correlations can be measured indirectly in terms of photon
correlations of the cavity mode