Cosmological coincidence without fine tuning

Lee, Joohan; Overduin, James; Lee, Tae Hoon; Oh, Phillial

doi:10.1103/physrevd.90.123003

Cited by 23 publications

(23 citation statements)

References 49 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As last step in our formal development, we wish to formulate QND measurement ofĤ as measurement continuous in time [34][35][36][37]. Physically, this amounts to making frequent and, in a continuum limit, continuous readouts X(t) of the meter variableX, with the quantum manybody system evolving according to (2).…”

Section: Qnd Measurement Ofĥmentioning

confidence: 99%

Quantum non-demolition measurement of a many-body Hamiltonian

et al. 2020

View full text Add to dashboard Cite

An ideal quantum measurement collapses the wave function of a quantum system to an eigenstate of the measured observable, with the corresponding eigenvalue determining the measurement outcome. For a quantum non-demolition (QND) observable, i.e., one that commutes with the Hamiltonian generating the system's time evolution, repeated measurements yield the same result, corresponding to measurements with minimal disturbance. This concept applies universally to single quantum particles as well as to complex many-body systems. However, while QND measurements of systems with few degrees of freedom has been achieved in seminal quantum optics experiments, it is an open challenge to devise QND measurement of a complex many-body observable. Here, we describe how a QND measurement of the Hamiltonian of an interacting many-body system can be implemented in a trapped-ion analog quantum simulator. Through a single shot measurement, the many-body system is prepared in a narrow energy band of (highly excited) energy eigenstates, and potentially even a single eigenstate. Our QND scheme, which can be carried over to other platforms of quantum simulation, provides a novel framework to investigate experimentally fundamental aspects of equilibrium and non-equilibrium statistical physics including the eigenstate thermalization hypothesis (ETH) and quantum fluctuation relations.

show abstract

Section: Qnd Measurement Ofĥmentioning

confidence: 99%

Quantum non-demolition measurement of a many-body Hamiltonian

et al. 2020

View full text Add to dashboard Cite

show abstract

“…The quantum scanning microscope [1] continuously measures the atomic density within its focal region of subwavelength size via dispersive coupling of atoms to a laser driven cavity, while the light reflected from the cavity is monitored by a homodyne detection within the framework of weak continuous measurements [3][4][5]. It builds on the idea of using the atom-cavity coupling for measurement and control of atomic quantum systems, which was employed in experiments [6,7] as well as in theoretical proposals [8][9][10][11][12][13]. The microscope achieves the spatial super-resolution by entangling the internal state of an atom with its position via engineering a spatially dependent dark state [14,15] (see Refs.…”

Section: Introductionmentioning

confidence: 99%

Quantum scanning microscope for cold atoms

Yang¹,

Vasilyev²,

Laflamme³

et al. 2018

Phys. Rev. A

View full text Add to dashboard Cite

We present a detailed theoretical description of a recently proposed atomic scanning microscope in a cavity QED setup [D. Yang et al., Phys. Rev. Lett. 120, 133601 (2018)]. The microscope continuously observes atomic densities with optical subwavelength resolution in a nondestructive way. The super-resolution is achieved by engineering an internal atomic dark state with a sharp spatial variation of population of a ground level dispersively coupled to the cavity field. Thus, the atomic position encoded in the internal state is revealed as a phase shift of the light reflected from the cavity in a homodyne experiment. Our theoretical description of the microscope operation is based on the stochastic master equation describing the conditional time evolution of the atomic system under continuous observation as a competition between dynamics induced by the Hamiltonian of the system, decoherence effects due to atomic spontaneous decay, and the measurement backaction. Within our approach we relate the observed homodyne current with a local atomic density, and discuss the emergence of a quantum nondemolition measurement regime allowing continuous observation of spatial densities of quantum motional eigenstates without measurement backaction in a single experimental run.

show abstract

“…Weak measurements constitute a source of competition with unitary dynamics [66,67,82,83], which is well seen in quantum trajectories formalism [6,[84][85][86][87][88][89], underlining the distinction between measurements and dissipation. Thus they can affect phase transitions, including the many-body ones [66,90,91].…”

mentioning

confidence: 99%

Feedback-Induced Quantum Phase Transitions Using Weak Measurements

et al. 2020

View full text Add to dashboard Cite

We show that applying feedback and weak measurements to a quantum system induces phase transitions beyond the dissipative ones. Feedback enables controlling essentially quantum properties of the transition, i.e., its critical exponent, as it is driven by the fundamental quantum fluctuations due to measurement. Feedback provides the non-Markovianity and nonlinearity to the hybrid quantumclassical system, and enables simulating effects similar to spin-bath problems and Floquet time crystals with tunable long-range (long-memory) interactions.

show abstract

Cosmological coincidence without fine tuning

Cited by 23 publications

References 49 publications

Quantum non-demolition measurement of a many-body Hamiltonian

Quantum non-demolition measurement of a many-body Hamiltonian

Quantum scanning microscope for cold atoms

Feedback-Induced Quantum Phase Transitions Using Weak Measurements

Contact Info

Product

Resources

About