Quantum Mechanics in the Negative Mass Reference Frame

Informations projet

QUANTUM-N

N° de convention de subvention: 787520

DOI

10.3030/787520

Projet clôturé

Date de signature de la CE 30 Mai 2018

Date de début 1 Juillet 2018

Date de fin 30 Juin 2023

Financé au titre de

• EXCELLENT SCIENCE - European Research Council (ERC)

Coût total

€ 2 178 574,00

Contribution de l’UE

€ 2 178 574,00

Coordonné par

KOBENHAVNS UNIVERSITET
Denmark

Periodic Reporting for period 4 - QUANTUM-N (Quantum Mechanics in the Negative Mass Reference Frame)

Période du rapport: 2023-01-01 au 2023-06-30

Résumé du contexte et des objectifs généraux du projet

A fundamental aspect of quantum mechanics is the balance between information and disturbance by the measurement. A
textbook example is the measurement of a position of an object which imposes a random perturbation on its momentum.
This perturbation, the quantum back action, translates with time into uncertainty of the motion trajectory. The PI has
proposed an approach which allows for simultaneous measurements of arbitrary small disturbances in both the position
and the momentum. It is based on a measurement performed in a quantum reference frame with an effective negative
mass, or frequency for an oscillator. The PI’s group has experimentally demonstrated the first step along this novel
path - quantum back action evasion for the measurement of motion in a reference frame of a spin oscillator.
This project takes detection of motion to a new frontier. We develop a novel hybrid quantum system
involving disparate macroscopic objects, a mechanical oscillator and a reference spin oscillator with the effective negative
mass. We will demonstrate quantum entanglement between the two oscillators and entanglement-enhanced sensing of
force and acceleration. The technology for high quality mechanical and spin oscillators developed at the PI’s group will be
further advanced towards those goals.
We will generate manifestly non-classical states of millimetre size mechanical oscillators and a macroscopic coherent
superposition of distant spin and mechanical objects. We will furthermore work towards generation of multi-partite
entangled states of spins, macroscopic objects, and photons, thus testing fundamental limits of entanglement and
decoherence for large and complex systems.
Gravitational wave interferometers which have recently detected first gravitational waves are expected to be soon limited in
their sensitivity by the quantum back action. The way to overcome this limit using the approach developed within this
project will be explored.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

1). Generation of a range of entangled states of two distant and disparate macroscopic objects
- a novel approach towards entanglement generation between those two macroscopic systems
- generation of an entangled state of a mechanical oscillator, a mm-size dielectric membrane and an
atomic spin oscillator built of 100 million atoms. Nature Physics, highlighted in by Nature News and Views and other outlets.
2). Demonstration of the measurement of force and acceleration beyond the standard quantum limit
of sensitivity.
- transduction of electric and magnetic signals to the optical domain, magnetocardiography on an isolated animal
heart, magnetic resonance imaging and detection of low-conductivity objects with an optical magnetometer.
3). Observation of macroscopic superposition states of moving millimetre size objects is fundamental for testing the limits of quantum theory.
- a macroscopic object, a mm size dielectric membrane, is cooled close to near absolute zero temperature
- photon scattering signifying the processes of adding and subtracting a single motional phonon
- a single spin excitation in a macroscopic ensembles of room temperature atoms.
4). Feasibility studies of application of the negative mass idea to multipartite entanglement involving
spins, photons and massive objects such as mirrors of gravitational wave interferometers.
- development of a "negative-mass quantum noise eater" which can be used for the proof-of-principle demonstration of enhanced sensitivity of
gravitational wave interferometers (GWIs), such as LIGO
- a magnetic "negative mass" oscillator in the quantum regime, and a source of entangled light which couples to the atomic negative mass system and to the GWI
A new idea paves the way towards experimentally feasible implementation of the negative mass atomic system.
5) We have demonstrated a macroscopic superposition state within a macroscopic atomic object and used it as a single photon source with built-in memory.
6) The first evidence of a single quantum excitation (Fock state) of motion of a macroscopic object is observed
7) We have invented and demonstrated magnetic induction tomography with an atomic ensemble in a quantum squeezed state providing an enhanced sensitivity to detection of weakly conducting objects

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

1). Generation of a range of entangled states of two distant and disparate macroscopic objects, the
mechanical oscillator and the atomic spin oscillator.
We have developed theoretically a novel approach towards entanglement generation between those two
macroscopic systems.
We have successfully achieved one of the major goals of this project: generation of an entangled state of a mechanical oscillator, a mm-size dielectric membrane and an atomic spin oscillator built of 100 million atoms. The entangled state spreads over a meter-scale distance and marks a new frontier in macroscopic entanglement.

2). Demonstration of the measurement of force and acceleration beyond the standard quantum limit
of sensitivity.
A general approach to measurements of force and acceleration beyond the standard quantum limit using a negative mass oscillator has been proposed.

3). Observation of macroscopic superposition states of moving millimetre size objects.
We have observed non-classical correlations between a photon generating a single phonon excitation and a subsequently delayed read-out of this phonon onto another photon. Non-classical correlations between the “write” and “read” photons have been observed (manuscript in preparation).
In a parallel effort we have made progress with the demonstration of a Fock state (single spin excitation) in a macroscopic ensembles of room temperature atoms. This work culminated in demonstration of a room temperature source of single photons with built-in memory.

4). Feasibility studies of application of the negative mass idea to multipartite entanglement involving
spins, photons and massive objects such as mirrors of gravitational wave interferometers.
We have demonstrated a "negative-mass quantum noise eater" which can be used for the proof-of-principle demonstration of enhanced sensitivity of gravitational wave interferometers, such as LIGO.
A new idea paves the way towards experimentally feasible implementation of the negative mass atomic system in the acoustic frequency range of gravitational waves.
In the next step we have demonstrated entanglement between the Caesium wavelength 852nm and 1064 nm light used in GWDs.

Finally, we have demonstrated the atomic negative-mass quantum noise eater based on room temperature atomic ensemble operating in a broad range of frequencies near the acoustic range suitable for GWDs (available online arXiv:2303.11029) accepted by Nature Comm.

5), In a new and unforeseen development, we have invented and demonstrated magnetic induction tomography with an atomic ensemble in a quantum squeezed state providing an enhanced sensitivity to detection of weakly conducting objects. This new direction in quantum sensing has promising potential applications in bio-medical sensing.

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