139 research outputs found
Experimental Test of an Event-Based Corpuscular Model Modification as an Alternative to Quantum Mechanics
We present the first experimental test that distinguishes between an
event-based corpuscular model (EBCM) [H. De Raedt et al.: J. Comput. Theor.
Nanosci. 8 (2011) 1052] of the interaction of photons with matter and quantum
mechanics. The test looks at the interference that results as a single photon
passes through a Mach-Zehnder interferometer [H. De Raedt et al.: J. Phys. Soc.
Jpn. 74 (2005) 16]. The experimental results, obtained with a low-noise
single-photon source [G. Brida et al.: Opt. Expr. 19 (2011) 1484], agree with
the predictions of standard quantum mechanics with a reduced of 0.98
and falsify the EBCM with a reduced of greater than 20
On the reconstruction of diagonal elements of density matrix of quantum optical states by on/off detectors
We discuss a scheme for reconstructing experimentally the diagonal elements
of the density matrix of quantum optical states. Applications to PDC heralded
photons, multi-thermal and attenuated coherent states are illustrated and
discussed in some details.Comment: 10 pages, presented at Palermo "TQMFA2005" Conference. To appear on
"Open Systems & Information Dynamics" (2006
Optimal estimation of entanglement and discord in two-qubit states
Recently, the fast development of quantum technologies led to the need for
tools allowing the characterization of quantum resources. In particular, the
ability to estimate non-classical aspects, e.g. entanglement and quantum
discord, in two-qubit systems, is relevant to optimise the performance of
quantum information processes. Here we present an experiment in which the
amount of entanglement and discord are measured exploiting different
estimators. Among them, some will prove to be optimal, i.e., able to reach the
ultimate precision bound allowed by quantum mechanics. These estimation
techniques have been tested with a specific family of states ranging from
nearly pure Bell states to completely mixed states. This work represents a
significant step in the development of reliable metrological tools for quantum
technologies
Improved implementation of nonclassicality test for a single particle
Recently a test of nonclassicality for a single qubit was proposed [R. Alicki
and N. Van Ryn, J. Phys. A: Math. Theor. 41, 062001 (2008)]. We present an
optimized experimental realization of this test leading to a 46 standard
deviation violation of classicality. This factor of 5 improvement over our
previous result was achieved by moving from the infrared to the visible where
we can take advantage of higher efficiency and lower noise photon detectors.Comment: 4 pages, 1 figur
Anomalous Weak Values and the Violation of a Multiple-measurement Leggett-Garg Inequality
Quantum mechanics presents peculiar properties that, on the one hand, have
been the subject of several theoretical and experimental studies about its very
foundations and, on the other hand, provide tools for developing new
technologies, the so-called quantum technologies. The nonclassicality pointed
out by Leggett-Garg inequalities has represented, with Bell inequalities, one
of the most investigated subject. In this letter we study the connection of
Leggett-Garg inequalities with a new emerging field of quantum measurement, the
weak values. In particular, we perform an experimental study of the four-time
correlators Legget-Garg test, by exploiting single and sequential weak
measurements performed on heralded single photons. We show violation of a
four-parameters Leggett-Garg inequality in different experimental conditions,
demonstrating an interesting connection between Leggett-Garg inequality
violation and anomalous weak values
Temporal teleportation with pseudo-density operators: how dynamics emerges from temporal entanglement
We show that, by utilising temporal quantum correlations as expressed by
pseudo-density operators (PDOs), it is possible to recover formally the
standard quantum dynamical evolution as a sequence of teleportations in time.
We demonstrate that any completely positive evolution can be formally
reconstructed by teleportation with different temporally correlated states.
This provides a different interpretation of maximally correlated PDOs, as
resources to induce quantum time-evolution. Furthermore, we note that the
possibility of this protocol stems from the strict formal correspondence
between spatial and temporal entanglement in quantum theory. We proceed to
demonstrate experimentally this correspondence, by showing a multipartite
violation of generalised temporal and spatial Bell inequalities and verifying
agreement with theoretical predictions to a high degree of accuracy, in
high-quality photon qubits.Comment: preprin
Temporal teleportation with pseudo-density operators: How dynamics emerges from temporal entanglement
open8We show that, by using temporal quantum correlations as expressed by pseudo-density operators (PDOs), it is possible to recover formally the standard quantum dynamical evolution as a sequence of teleportations in time. We demonstrate that any completely positive evolution can be formally reconstructed by teleportation with different temporally correlated states. This provides a different interpretation of maximally correlated PDOs, as resources to induce quantum time evolution. Furthermore, we note that the possibility of this protocol stems from the strict formal correspondence between spatial and temporal entanglement in quantum theory. We proceed to demonstrate experimentally this correspondence, by showing a multipartite violation of generalized temporal and spatial Bell inequalities and verifying agreement with theoretical predictions to a high degree of accuracy, in high-quality photon qubits.openMarletto, C; Vedral, V; Virzi', S; Avella, A; Piacentini, F; Gramegna, M; Degiovanni, IP; Genovese, MMarletto, C; Vedral, V; Virzi', S; Avella, A; Piacentini, F; Gramegna, M; Degiovanni, Ip; Genovese,
Mode structure reconstruction by detected and undetected light
We introduce a novel technique for the reconstruction of multimode optical
fields, based on simultaneously exploiting both the generalized Glauber's
-order correlation function and a recently proposed
anti-correlation function (dubbed ) which is resilient to
Poissonian noise. We experimentally demonstrate that this method yields mode
reconstructions with higher fidelity with respect to those obtained with
reconstruction methods based only on 's, even requiring less "a
priori" information. The reliability and versatility of our technique make it
suitable for a widespread use in real applications of optical quantum
measurement, from quantum information to quantum metrology, especially when one
needs to characterize ensembles of single-photon emitters in the presence of
background noise (due, for example, to residual excitation laser, stray light,
or unwanted fluorescence).Comment: 11 pages, 3 figure
Quantum characterization of superconducting photon counters
We address the quantum characterization of photon counters based on
transition-edge sensors (TESs) and present the first experimental tomography of
the positive operator-valued measure (POVM) of a TES. We provide the reliable
tomographic reconstruction of the POVM elements up to 11 detected photons and
M=100 incoming photons, demonstrating that it is a linear detector.Comment: 3 figures, NJP (to appear
- …