Quantum measurement and control of non-classical mechanical states

Projektinformationen

emcc

ID Finanzhilfevereinbarung: 101110196

DOI

10.3030/101110196

Projekt abgeschlossen

EK-Unterschriftsdatum 20 März 2023

Startdatum 1 Mai 2023

Enddatum 31 Mai 2025

Finanziert unter

• Marie Skłodowska-Curie Actions (MSCA)

Gesamtkosten

Keine Daten

EU-Beitrag

€ 230 774,40

Koordiniert durch

KOBENHAVNS UNIVERSITET
Denmark

Periodic Reporting for period 1 - emcc (Quantum measurement and control of non-classical mechanical states)

Berichtszeitraum: 2023-05-01 bis 2025-05-31

Zusammenfassung vom Kontext und den Gesamtzielen des Projekts

Mechanical resonators offer a promising platform for emerging quantum technologies—ranging from ultra-sensitive sensors and quantum transducers to fundamental tests of quantum mechanics—but preparing non-classical states of motion in macroscopic devices remains a key challenge due to thermal noise and limited measurement strength. The emcc project set out to overcome these barriers by developing and integrating quantum measurement and control techniques to engineer two hallmark non-classical states on millimetre-scale silicon-nitride membranes: first, a heralded single-phonon Fock state at cryogenic temperature; second, a quantum-squeezed state at room temperature. To verify these states, the project also aimed to implement full Wigner-function tomography, thereby demonstrating negative quasi-probabilities and unambiguously revealing non-classicality in a mesoscopic mechanical system.

Arbeit, die ab Beginn des Projekts bis zum Ende des durch den Bericht erfassten Berichtszeitraums geleistet wurde, und die wichtigsten bis dahin erzielten Ergebnisse

• 4 K optomechanical system fabrication and characterization (WP1 & 2): We assembled the membrane-in-the-middle cavity and achieved operation at 4 K. The fundamental mechanical mode’s quality factor (Q) was measured with 300 million, confirming ultracoherent performance suitable for quantum experiments.
• Photon-counting attempts for single-phonon generation (WP1): Using pulsed sideband photon counting on red and blue motional sidebands, we sought to herald single-phonon state generation. The photon statistics does not satisfy the single phonon threshold.
• Continuous-measurement protocol (WP1 & 2): To avoid the complexity of the pulsed scheme, we developed a new protocol that could be easier to achieve our goal. In partnership with Prof Klemens Hammerer, we developed a continuous measurement scheme that combines photocurrent monitoring with real-time photon counting. Detailed theoretical modeling of this hybrid approach has been completed, demonstrating its capability to produce heralded single-phonon states and enable full Wigner-function tomography (see Fig. 1.). Experimental implementation is underway.
• Squeezing project (WP3): We finalized a comprehensive theoretical analysis of measurement-based feedback squeezing at room temperature. A preprint detailing the physics and experimental feasibility has been posted on arXiv:2402.17460; manuscript submission to a peer-reviewed journal is in preparation.

Fortschritte, die über den aktuellen Stand der Technik hinausgehen und voraussichtliche potenzielle Auswirkungen (einschließlich der bis dato erzielten sozioökonomischen Auswirkungen und weiter gefassten gesellschaftlichen Auswirkungen des Projekts)

• Ultracoherent 4 K platform: The optomechanical parameters characterization such as Q-factor measurement at cryogenic temperature validates a mesoscopic mechanical device for quantum applications, extending beyond previous work by confirming coherence at a few kelvin.
• Novel continuous-measurement protocol: Our theoretical proposal uniquely fuses continuous photocurrent detection with discrete photon-counting events to herald non-Gaussian mechanical states without disruptive pulsed drives. This hybrid method offers a scalable route to single-phonon preparation and tomography in macroscopic systems—surpassing existing pulsed-only schemes.
• Room-temperature squeezing feasibility: The arXiv preprint presents the first detailed feasibility study showing that continuous measurement and feedback can yield mechanical variance below the zero-point level at ambient conditions, opening prospects for cryogen-free quantum sensors.