Search results for "Quantum physic"
showing 10 items of 1596 documents
Towards Rydberg quantum logic with trapped ions
2016
We demonstrate the excitation of ions to the Rydberg state $22F$ by vacuum ultraviolet radiation at a wavelength of $123\,\text{nm}$ combined with the coherent manipulation of the optical qubit transition in $^{40}\text{Ca}^+$. With a tightly focused beam at $729\,\text{nm}$ wavelength we coherently excite a single ion from a linear string into the metastable $3D_{5/2}$ state before a VUV pulse excites it to the Rydberg state. In combination with ion shuttling in the trap, we extend this approach to the addressed excitation of multiple ions. The coherent initialization as well as the addressed Rydberg excitation are key prerequisites for more complex applications of Rydberg ions in quantum …
Detection of missing low-lying atomic states in actinium
2020
Two lowest-energy odd-parity atomic levels of actinium, 7s^27p 2P^o_1/2, 7s^27p 2P^o_3/2, were observed via two-step resonant laser-ionization spectroscopy and their respective energies were measured to be 7477.36(4) cm^-1 and 12 276.59(2) cm^-1. The lifetimes of these states were determined as 668(11) ns and 255(7) ns, respectively. In addition, these properties were calculated using a hybrid approach that combines configuration interaction and coupled-cluster methods in good agreement. The data are of relevance for understanding the complex atomic spectra of actinides and for developing efficient laser-cooling and ionization schemes for actinium, with possible applications for high-purity…
Relating quantum incoherence, entanglement and superluminal signalling
2020
Hereby we inspect two-partite entanglement using thought experiment that relates properties of incoherently mixed states to the impossibility of faster-than-light (FTL) signalling. We show that if there appears a way to distinguish ensembles of particles that are described by the same density matrix, but are generated using different pure states - properties of entanglement (namely, non-classical correlations) could be employed to create an FTL signalling device. We do not claim FTL signalling is possible, rather, we establish the logical connection between the aforementioned properties of current physical theory which has not so far been evident.
Robust quantum control by shaped pulse
2013
Considering the problem of the control of a two-state quantum system by an external field, we establish a general and versatile method that allows the derivation of smooth pulses, suitable for ultrafast applications, that feature the properties of high-fidelity, robustness, and low area. Such shaped pulses can be viewed as a single-shot generalization of the composite pulse technique with a time-dependent phase.
FitAik: a package to calculate least-square fitted atomic transitions probabilities. Application to the Er+ lanthanide ion
2022
We present a new method implemented in our new package \textit{FitAik}, to perform least-squares fitting of calculated and experimental atomic transition probabilities, by using the mono-electronic transition integrals $\langle n\ell |r| n'\ell' \rangle$ (with $r$ the electronic radial coordinate) as adjustable quantities. \textit{FitAik} is interfaced to the Cowan suite of codes, for which it automatically writes input files and reads output files. We illustrate our procedure with the example of Er$^{+}$ ion, for which the agreement between calculated and experimental Einstein coefficients is found to be very good. The source code of \emph{FitAik} can be found on GitLab, and the calculated…
A Possible Time-Dependent Generalization of the Bipartite Quantum Marginal Problem
2018
In this work we study an inverse dynamical problem for a bipartite quantum system governed by the time local master equation: to find the class of generators which give rise to a certain time evolution with the constraint of fixed reduced states (marginals). The compatibility of such choice with a global unitary evolution is considered. For the non unitary case we propose a systematic method to reconstruct examples of master equations and address them to different physical scenarios.
Necessary and Sufficient Conditions for an Extended Noncontextuality in a Broad Class of Quantum Mechanical Systems
2015
The notion of (non)contextuality pertains to sets of properties measured one subset (context) at a time. We extend this notion to include so-called inconsistently connected systems, in which the measurements of a given property in different contexts may have different distributions, due to contextual biases in experimental design or physical interactions (signaling): a system of measurements has a maximally noncontextual description if they can be imposed a joint distribution on in which the measurements of any one property in different contexts are equal to each other with the maximal probability allowed by their different distributions. We derive necessary and sufficient conditions for th…
Properties and application of nondeterministic quantum query algorithms
2006
Many quantum algorithms can be analyzed in a query model to compute Boolean functions where input is given by a black box. As in the classical version of decision trees, different kinds of quantum query algorithms are possible: exact, zero-error, bounded-error and even nondeterministic. In this paper, we study the latter class of algorithms. We introduce a fresh notion in addition to already studied nondeterministic algorithms and introduce dual nondeterministic quantum query algorithms. We examine properties of such algorithms and prove relations with exact and nondeterministic quantum query algorithm complexity. As a result and as an example of the application of discovered properties, we…
Nonclassicality detection from few Fock-state probabilities
2020
We devise a new class of criteria to certify the nonclassicality of photon- and phonon-number statistics. Our criteria extend and strengthen the broadly used Klyshko's criteria, which require knowledge of only a finite set of Fock-state probabilities. This makes the criteria well-suited to experimental implementation in realistic conditions. Moreover, we prove the completeness of our method in some scenarios, showing that, when only two or three Fock-state probabilities are known, it detects all finite distributions incompatible with classical states. In particular, we show that our criteria detect a broad class of noisy Fock states as nonclassical, even when Klyshko's do not. The method is…
Sensitive magnetometry in challenging environments
2020
State-of-the-art magnetic field measurements performed in shielded environments under carefully controlled conditions rarely reflect the realities of those applications envisioned in the introductions of peer-reviewed publications. Nevertheless, significant advances in magnetometer sensitivity have been accompanied by serious attempts to bring these magnetometers into the challenging working environments in which they are often required. This review discusses the ways in which various (predominantly optically pumped) magnetometer technologies have been adapted for use in a wide range of noisy and physically demanding environments.