Single-Atom Single-Photon Quantum Interface

Abstract

tors (17). The resulting density matrix has only positive eigenvalues, and hence it represents a physically possible state. Its fidelity with respect to the expected Bell state, |Y-〉 from Eq. 2, is F = 86.0(4)%, with 0.5 < F ≤ 1 proving entan-glement (18). From the density matrix, following (16), we derive a concurrence of C = 0.73(7), with 0 < C ≤ 1 also proving entanglement. Because of technical imperfections, e.g., of polarizers in the detection setups, the observed fidelity/concurrence sets a lower bound for both the atom-photon and photon-photon entangle-ment achieved. The same measurements were done for B = −0.13 G and t S = 2.8 ms for which the atomic superposition state accumulates a p phase shift (compare to Fig. 3). Therefore, a density matrix corresponding to the Bell state jY þ 〉 ≡ 1 ffiffi 2 p ðjþ1; s − 〉 þ j−1; s þ 〉Þ is expected. This is indeed observed (Fig. 4B) with a fidelity of F = 82.9(6)% and a concurrence of C = 0.72(13). The state evolves between the two photon detections as a result of the constant magnetic field. Future experiments could produce a time-independent |Y + 〉 Bell state by applying a pulsed magnetic field to the atom between entanglement generation and state mapping. Moreover, partial driving of the Raman transition in combination with atomic state manipulation should allow production of highly entangled multiphoton states (12). Our technique applied to a quasi-permanently trapped intracavity atom (3, 19) will push the probability of success even further, making the scheme truly deterministic. Two (or more) such systems operated in parallel are perfectly suited for teleportation and entanglement experiments in a quantum network (20-22) or quantum gate operations in a distributed and, hence, scalable quantum computer (23, 24). Inorganic porous materials are being developed for use as molecular sieves, ion exchangers, and catalysts, but most are oxides. We show that various sulfide and selenide clusters, when bound to metal ions, yield gels having porous frameworks. These gels are transformed to aerogels after supercritical drying with carbon dioxide. The aerogels have high internal surface area (up to 327 square meters per gram) and broad pore size distribution, depending on the precursors used. The pores of these sulfide and selenide materials preferentially absorb heavy metals. These materials have narrow energy gaps (between 0.2 and 2.0 electron volts) and low densities, and they may be useful in optoelectronics, as photocatalysts, or in the removal of heavy metals from water. I norganic porous materials are at the foundation of broad applications such as molecular sieves, ion exchangers, and catalysts (1, 2). Zeolites and aluminosilicate mesoporous materials constitute the vast majority of this class. Aerogels are another kind of porous inorganic amorphous polymer in which nanosized blocks are interconnected to yield high internal surface area, very low densities, and large open pores (3, 4). Although the sol-gel chemistry of oxide-based materials (e.g., SiO 2 , Al 2 O 3 ,...

Sequential measurement-based quantum computing with memories

“…For example, cavity quantum-electrodynamics (QED) atom-photon interfaces [18,19] are perfectly-suited for our scheme in FIG. 4: Sequential MBQC in 2D can be carried out assuming that it is possible to build one of the graph states from the left side.…”

“…In a dual way, ground states of static atoms inside optical cavities can be used to encode the memories, and single photons emitted from them the flying registers [19][20][21]. Also artificial-atomphoton interfaces can be used analogously, as for instance quantum-dot [22] and circuit-QED [23] architectures.…”

Novel Ion Trap Design for Strong Ion-Cavity Coupling

“…For example, in the optical domain the generation of single photons [1], entanglement between single atoms and single photons [2] and the transfer of quantum states between two remote atoms [3] have been demonstrated using neutral atoms strongly coupled to optical cavities. On the other hand, employing ionized atoms instead offers clear advantages such as robust trapping and precise quantum state control [4].…”

Interparticle Coupling Effects of Two Quantum Dots System on the Transport Properties of a Single Plasmon

“…Photons can be regarded as ideal carriers of quantum information, therefore manipulating photons could have important applications in quantum computation and quantum information technology [6][7][8]. However, photons rarely interact with each other, thus we have to explore the ways how to control the photons with the photon-atom interaction.…”