It is important for performance studies in quantum technologies to analyze quantum circuits in the presence of noise. We introduce an error probability tensor, a tool to track generalized Pauli error statistics of qudits within quantum circuits composed of qudit Clifford gates. Our framework is compatible with qudit stabilizer quantum error-correcting codes. We show how the error probability tensor can be applied in the most general case, and we demonstrate an error analysis of bipartite qudit repeaters with quantum error correction. We provide an exact analytical solution of the error statistics of the state distributed by such a repeater. For a fixed number of degrees of freedom, we observe that higher-dimensional qudits can outperform qubits in terms of distributed entanglement. arXiv:1807.06030v1 [quant-ph]
In a hybrid optomechanical setup consisting of a two-level atom in a cavity with a pendular end-mirror, the interplay between the light field's radiation pressure on the mirror and the dipole interaction with the atom can lead to an effect, which manifests itself in the suppression of Rabi oscillations of the atomic population. This effect is present when the system is in the single-photon strong coupling regime and has an analogy in the photon blockade of optomechanics.
A quantum well (QW) in the presence of a homogeneous electric field forms a system with continuous energy spectrum. Its density of states (DOS) is calculated. A general DOS formula is applied which avoids the well-known difficulties for systems with continuous spectra. The Schrodinger equation is solved exactly, and the 1D DOS is expressed in closed analytical form by means of Airy functions of first and second kind. Quasistationary energy levels are defined as zeros of a certain 4 x 4 matrix. Their positions are calculated in dependence on the field strength over a wide range. The 1D DOS peaks arising from quasistationary levels are studied for different field strengths. The same is done for the 1D DOS in a larger energy interval ranging from far below the QW bottom up to far above the QW barriers. Franz-Keldysh oscillations as well as QW interferences are observed above the barriers.Ein Quantum-Well (QW) im homogenen elektrischen Feld ist ein System mit kontinuierlichem Energiespektrum. Seine Zustandsdichte (DOS) wird berechnet. Dabei wird eine allgemeine DOS Formel verwendet, die die bekannten Schwierigkeiten vermeidet, die bei Systemen mit kontinuierlichem Energiespektrum auftreten. Die Schrodinger-Gleichung wird exakt gelost, und die 1D DOS wird in geschlossener analytischer Form durch Airy-Funktionen erster und zweiter Art ausgedruckt. Quasistationiire Energieniveaus werden als Nullstellen einer gewissen 4 x 4-Matrix definiert. Ihre Positionen in Abhangigkeit von der Feldstiirke werden in einem weiten Bereich berechnet. Die den quasistationiiren Niveaus entsprechenden Maxima der 1D DOS werden fur verschiedene Feldstlrken untersucht. Das gleiche wird durchgefuhrt fur die 1D DOS in einem grol3eren Energieintervall, das von weit unterhalb des QW-Bodens bis weit oberhalb der QW-Barrieren reicht. Fur Energien oberhalb der Barrieren werden Franz-Keldysh-Oszillationen und QW-Interferenzen beobachtet.
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