Search results for "Quantum physic"
showing 10 items of 1596 documents
Creation, storage, and on-demand release of optical quantum states with a negative Wigner function
2013
Highly nonclassical quantum states of light, characterized by Wigner functions with negative values, have been created so far only in a heralded fashion. In this case, the desired output emerges rarely and randomly from a quantum-state generator. An important example is the heralded production of high-purity single-photon states, typically based on some nonlinear optical interaction. In contrast, on-demand single-photon sources were also reported, exploiting the quantized level structure of matter systems. These sources, however, lead to highly impure output states, composed mostly of vacuum. While such impure states may still exhibit certain single-photon-like features such as anti-bunchin…
Polarimetric measurements of single-photon geometric phases
2014
We report polarimetric measurements of geometric phases that are generated by evolving polarized photons along non-geodesic trajectories on the Poincar\'e sphere. The core of our polarimetric array consists of seven wave plates that are traversed by a single photon beam. With this array any SU(2) transformation can be realized. By exploiting the gauge invariance of geometric phases under U(1) local transformations, we nullify the dynamical contribution to the total phase, thereby making the latter coincide with the geometric phase. We demonstrate our arrangement to be insensitive to various sources of noise entering it. This makes the single-beam, polarimetric array a promising, versatile t…
Experimental Quantum Probing Measurements With No Knowledge on the System-Probe Interaction
2020
In any natural science, measurements are the essential link between theory and observable reality. Is it possible to obtain accurate and relevant information via measurement whose action on the probed system is unknown? In other words, can one be convinced to know something about the nature without knowing in detail how the information was obtained? In this paper, we show that the answer is surprisingly, yes. We construct and experimentally implement a quantum optical probing measurement where measurements on the probes, the photons' polarization states, are used to extract information on the systems, the frequency spectra of the same photons. Unlike the pre-existing probing protocols, our …
Characterization of the global network of optical magnetometers to search for exotic physics (GNOME)
2018
The Global Network of Optical Magnetometers to search for Exotic physics (GNOME) is a network of geographically separated, time-synchronized, optically pumped atomic magnetometers that is being used to search for correlated transient signals heralding exotic physics. The GNOME is sensitive to nuclear- and electron-spin couplings to exotic fields from astrophysical sources such as compact dark-matter objects (for example, axion stars and domain walls). Properties of the GNOME sensors such as sensitivity, bandwidth, and noise characteristics are studied in the present work, and features of the network's operation (e.g., data acquisition, format, storage, and diagnostics) are described. Charac…
Dynamics of an unbalanced two-ion crystal in a Penning trap for application in optical mass spectrometry
2019
In this article, the dynamics of an unbalanced two-ion crystal comprising the 'target' and the 'sensor' ions confined in a Penning trap has been studied. First, the low amplitude regime is addressed. In this regime, the overall potential including the Coulomb repulsion between the ions can be considered harmonic and the axial, magnetron and reduced-cyclotron modes split up into the so-called 'stretch' and 'common' modes, that are generalizations of the well-known 'breathing' and 'center-of-mass' motions of a balanced crystal made of two ions. By measuring the frequency modes of the crystal and the sensor ion eigenfrequencies using optical detection, it will be possible to determine the targ…
Surpassing the Energy Resolution Limit with Ferromagnetic Torque Sensors
2021
We discuss the fundamental noise limitations of a ferromagnetic torque sensor based on a levitated magnet in the tipping regime. We evaluate the optimal magnetic field resolution taking into account the thermomechanical noise and the mechanical detection noise at the standard quantum limit (SQL). We find that the Energy Resolution Limit (ERL), pointed out in recent literature as a relevant benchmark for most classes of magnetometers, can be surpassed by many orders of magnitude. Moreover, similarly to the case of a ferromagnetic gyroscope, it is also possible to surpass the standard quantum limit for magnetometry with independent spins, arising from spin-projection noise. Our finding indica…
Relations between entanglement and purity in non-Markovian dynamics
2016
Knowledge of the relationships among different features of quantumness, like entanglement and state purity, is important from both fundamental and practical viewpoints. Yet, this issue remains little explored in dynamical contexts for open quantum systems. We address this problem by studying the dynamics of entanglement and purity for two-qubit systems using paradigmatic models of radiation-matter interaction, with a qubit being isolated from the environment (spectator configuration). We show the effects of the corresponding local quantum channels on an initial two-qubit pure entangled state in the concurrence-purity diagram and find the conditions which enable dynamical closed formulas of …
Pseudo-fermions in an electronic loss-gain circuit
2013
In some recent papers a loss-gain electronic circuit has been introduced and analyzed within the context of PT-quantum mechanics. In this paper we show that this circuit can be analyzed using the formalism of the so-called pseudo-fermions. In particular we discuss the time behavior of the circuit, and we construct two biorthogonal bases associated to the Liouville matrix $\Lc$ used in the treatment of the dynamics. We relate these bases to $\Lc$ and $\Lc^\dagger$, and we also show that a self-adjoint Liouville-like operator could be introduced in the game. Finally, we describe the time evolution of the circuit in an {\em Heisenberg-like} representation, driven by a non self-adjoint hamilton…
A deeper insight into quantum state transfer from an information flux viewpoint
2008
We use the recently introduced concept of information flux in a many-body register in order to give an alternative viewpoint on quantum state transfer in linear chains of many spins.
Stroboscopic aliasing in long-range interacting quantum systems
2021
We unveil a mechanism for generating oscillations with arbitrary multiplets of the period of a given external drive, in long-range interacting quantum many-particle spin systems. These oscillations break discrete time translation symmetry as in time crystals, but they are understood via two intertwined stroboscopic effects similar to the aliasing resulting from video taping a single fast rotating helicopter blade. The first effect is similar to a single blade appearing as multiple blades due to a frame rate that is in resonance with the frequency of the helicopter blades' rotation; the second is akin to the optical appearance of the helicopter blades moving in reverse direction. Analogously…