37 research outputs found
Projection of two biphoton qutrits onto a maximally entangled state
Bell state measurements, in which two quantum bits are projected onto a
maximally entangled state, are an essential component of quantum information
science. We propose and experimentally demonstrate the projection of two
quantum systems with three states (qutrits) onto a generalized maximally
entangled state. Each qutrit is represented by the polarization of a pair of
indistinguishable photons - a biphoton. The projection is a joint measurement
on both biphotons using standard linear optics elements. This demonstration
enables the realization of quantum information protocols with qutrits, such as
teleportation and entanglement swapping.Comment: 4 pages, 3 figures, published versio
Mid-circuit qubit measurement and rearrangement in a Yb atomic array
Measurement-based quantum error correction relies on the ability to determine
the state of a subset of qubits (ancillae) within a processor without revealing
or disturbing the state of the remaining qubits. Among neutral-atom based
platforms, a scalable, high-fidelity approach to mid-circuit measurement that
retains the ancilla qubits in a state suitable for future operations has not
yet been demonstrated. In this work, we perform imaging using a
narrow-linewidth transition in an array of tweezer-confined Yb atoms to
demonstrate nondestructive state-selective and site-selective detection. By
applying site-specific light shifts, selected atoms within the array can be
hidden from imaging light, which allows a subset of qubits to be measured while
causing only percent-level errors on the remaining qubits. As a
proof-of-principle demonstration of conditional operations based on the results
of the mid-circuit measurements, and of our ability to reuse ancilla qubits, we
perform conditional refilling of ancilla sites to correct for occasional atom
loss, while maintaining the coherence of data qubits. Looking towards true
continuous operation, we demonstrate loading of a magneto-optical trap with a
minimal degree of qubit decoherence.Comment: 9 pages, 6 figure
Delayed-Choice Experiments and the Metaphysics of Entanglement
Delayed-choice experiments in quantum mechanics are often taken to undermine a realistic interpretation of the quantum state. More specifically, Healey has recently argued that the phenomenon of delayed-choice entanglement swapping is incompatible with the view that entanglement is a physical relation between quantum systems. This paper argues against these claims. It first reviews two paradigmatic delayed-choice experiments and analyzes their metaphysical implications. It then applies the results of this analysis to the case of entanglement swapping, showing that such experiments pose no threat to realism about entanglement
Synthesis and evaluation of sphingosine analogues as inhibitors of sphingosine kinases
10.1021/jm900121dJournal of Medicinal Chemistry52123618-3626JMCM
N,N-dimethyl-D-erythro-sphingosine increases intracellular Ca2+ concentration via Na+-Ca2+-exchanger in HCT116 human colon cancer cells
Overcoming MDR-associated chemoresistance in HL-60 acute myeloid leukemia cells by targeting sphingosine kinase-1
We examined the involvement of sphingosine kinase-1, a critical regulator of the sphingolipid balance, in susceptibility to antineoplastic agents of either sensitive or multidrug-resistant acute myeloid leukemia cells. Contrary to parental HL-60 cells, doxorubicin and etoposide failed to trigger apoptosis in chemoresistant HL-60/Doxo and HL-60NP16 cells overexpressing MRP1 and MDR1, respectively. Chemosensitive HL-60 cells displayed sphingosine kinase-1 inhibition coupled with ceramide generation. In contrast, chemoresistant HL-60/ Doxo and HL-60/VP16 had sustained sphingosine kinase-1 activity and did not produce ceramide during treatment. Enforced expression of sphingosine kinase-1 in chemosensitive HL-60 cells resulted in marked inhibition of apoptosis that was mediated by blockade of mitochondrial cytochrome c efflux hence suggesting a control of apoptosis at the pre-mitochondrial level. Incubation with cell-permeable ceramide of chemoresistant cells led to a sphingosine kinase-1 inhibition and apoptosis both prevented by sphingosine kinase-1 over-expression. Furthermore, F-12509a, a new sphingosine kinase inhibitor, led to ceramide accumulation, decrease in sphingosine 1-phosphate content and caused apoptosis equally in chemosensitive and chemoresistant cell lines that is inhibited by adding sphingosine 1-phosphate or overexpressing sphingosine kinase-1. F-12509a induced classical apoptosis hallmarks namely nuclear fragmentation, caspase-3 cleavage as well as downregulation of antiapoptotic XIAP, and release of cytochrome c and SMAC/Diablo