11 research outputs found
Protective Measurement-A New Quantum Measurement Paradigm: Detailed Description of the First Realization
We present a detailed description of the experiment realizing for the first time a protective measurement, a novel measurement protocol which combines weak interactions with a "protection mechanism" preserving the measured state coherence during the whole measurement process. Furthermore, protective measurement allows finding the expectation value of an observable, i.e., an inherently statistical quantity, by measuring a single particle, without the need for any statistics. This peculiar property, in sharp contrast to the framework of traditional (projective) quantum measurement, might constitute a groundbreaking advance for several quantum technology related fields
Towards a standard procedure for the measurement of the multi-photon component in a CW telecom heralded single-photon source
Single-photon sources are set to be a fundamental tool for metrological
applications as well as for quantum information related technologies. Because
of their upcoming widespread dissemination, the need for their characterization
and standardization is becoming of the utmost relevance. Here, we illustrate a
strategy to provide a quantitative estimate of the multi-photon component of a
single-photon source, showing the results achieved in a pilot study for the
measurement of the second order autocorrelation function of a
low-noise CW heralded single-photon source prototype (operating at telecom
wavelength nm) realized in INRiM. The results of this pilot
study, involving PTB, NPL and INRiM, will help to build up a robust and
unambiguous procedure for the characterization of the emission of a
single-photon source
Protective measurement - a new quantum measurement paradigm: Detailed description of the first realization
We present a detailed description of the experiment realizing for the first time a protective measurement, a novel measurement protocol which combines weak interactions with a “protection mechanism” preserving the measured state coherence during the whole measurement process. Furthermore, protective measurement allows finding the expectation value of an observable, i.e., an inherently statistical quantity, by measuring a single particle, without the need for any statistics. This peculiar property, in sharp contrast to the framework of traditional (projective) quantum measurement, might constitute a groundbreaking advance for several quantum technology related fields
Quantum Measurements in weak coupling regime: from Sequential weak values to Protective measurements
Theoretical description and experimental simulation of quantum entanglement near open time-like curves via pseudo-density operators
10.1038/s41467-018-08100-1Nature Communications10118
Theoretical description and experimental simulation of quantum entanglement near open time-like curves via pseudo-density operators
Closed timelike curves are striking predictions of general relativity allowing for time-travel. They are afflicted by notorious causality issues (e.g. grandfather's paradox). Quantum models where a qubit travels back in time solve these problems, at the cost of violating quantum theory's linearity-leading e.g. to universal quantum cloning. Interestingly, linearity is violated even by open timelike curves (OTCs), where the qubit does not interact with its past copy, but is initially entangled with another qubit. Non-linear dynamics is needed to avoid violating entanglement monogamy. Here we propose an alternative approach to OTCs, allowing for monogamy violations. Specifically, we describe the qubit in the OTC via a pseudo-density operator-a unified descriptor of both temporal and spatial correlations. We also simulate the monogamy violation with polarization-entangled photons, providing a pseudo-density operator quantum tomography. Remarkably, our proposal applies to any space-time correlations violating entanglement monogamy, such as those arising in black holes
Non-monogamy of spatio-temporal correlations and the black hole information loss paradox
10.3390/e22020228Entropy22222
Protective measurements: Extracting the expectation value by measuring a single particle
In quantum mechanics, the eigenvalues and their corresponding probabilities specify the expectation value of a physical observable, which is known to be a statistical property related to large ensembles of particles. In contrast to this paradigm, we demonstrate a unique method allowing to extract the expectation value of a single particle, namely, the polarisation of a single protected photon, with a single experiment. This is the first realisation of quantum protective measurements