We demonstrate efficient storage and retrieval of light pulses by electromagnetically induced transparency (EIT) in a Pr^{3+}:Y_{2}SiO_{5} crystal. Using a ring-type multipass configuration, we increase the optical depth (OD) of the medium up to a factor of 16 towards OD≈96. Combining the large optical depth with optimized conditions for EIT, we reach a light storage efficiency of (76.3±3.5)%. In addition, we perform extended systematic measurements of the storage efficiency versus optical depth, control Rabi frequency, and probe pulse duration. The data confirm the theoretically expected behavior of an EIT-driven solid-state memory.

We experimentally demonstrate composite stimulated Raman adiabatic passage (CSTIRAP), which combines the concepts of composite pulse sequences and adiabatic passage. The technique is applied for population transfer in a rare-earth doped solid. We compare the performance of CSTIRAP with conventional single and repeated STIRAP, either in the resonant or the highly detuned regime. In the latter case, CSTIRAP improves the peak transfer efficiency and robustness, boosting the transfer efficiency substantially compared to repeated STIRAP. We also propose and demonstrate a universal version of CSTIRAP, which shows improved performance compared to the originally proposed composite version. Our findings pave the way towards new STIRAP applications, which require repeated excitation cycles, e.g., for momentum transfer in atom optics, or dynamical decoupling to invert arbitrary superposition states in quantum memories. arXiv:1811.05719v1 [quant-ph]

We introduce a method to rotate arbitrarily the excitation profile of universal broadband composite pulse sequences for robust high-fidelity population inversion. These pulses compensate deviations in any experimental parameter (e.g. pulse amplitude, pulse duration, detuning from resonance, Stark shifts, unwanted frequency chirp, etc.) and are applicable with any pulse shape. The rotation allows to achieve higher order robustness to any combination of pulse area and detuning errors at no additional cost. The latter can be particularly useful, e.g., when detuning errors are due to Stark shifts that are correlated with the power of the applied field. We demonstrate the efficiency and universality of these composite pulses by experimental implementation for rephasing of atomic coherences in a Pr 3+ :Y2SiO5 crystal.

IntroductionFor the replacement of conventional mass storage systems by semiconductor memory technologies very high density memories are demanded. A novel non-volatile semiconductor-memory technology called Record on Silicon (ROS) incorporating a vertical cell is aiming at this objective. Based on a cell size of about 3F2 (F denotes the minimum feature size), the technology is enabling an approximately twofold packing density compared to conventional, planar ROM and pushes into market segments for non-semiconductor memories in the multimedia arena. Relying on a 256M-DRAM technology, a 1 G ROMdevice is already within the reach of this technology The new type solid state memory chip is designed for use in notebooks, mobile phones, portable music players and in-car information systems, personal digital assistants and notebook computers.The key of the new technology is a cell concept based on a vertical MOS transistor in a trench which allow to use the bottom of the trench as additional, selfaligned tiitline and thus to double the bitline density. In the following, the new process, furtheron denoted as ROS-process, is described. First the process sequence is outlined, then the characteristic data of the key devices are given and finally the features of the ROS-technology are demonstrated by means of a 1 Mbit-ROM. Memory cell conceptIn order to issue a memory cell of half the size of a regular cross point cell, adjacent bitlines are not isolated from each other by a planar, Fsized spacing but by a vertical spacing, formed by the trench sidewall The bitlines on the surface and on the bottom of the trenches are selfaligned, the pitch of the bitlines can be halved. Consequently, the memory MOS-devices located in a NOR-configuration in between the bitlines are to be formed at the sidewalls of the trenches (Fig.la\ The area requirement of this memory cell is defined by the projection of this 3-D-configuration onto the wafer surface. Due to overlay tolerances and pattern transfer accuracies, the cell size amounts to about 3Fz which value has, to be compared to the approximately 5-6 Fz of the planar mask ROM cell. TechnologyFor test purposes, the vertical cell concept was integrated into the process pattern of a 0.!5 vm CMOS process used for the logic periphery of the ROM according to the process flow of Fig.2. Since the Vth of the vertical transistor has to be adjusted by the bulk dopant level [2], the process was started by p-well formation for the memory array, followed by CMOlS twin well formation and poly buffered LOCOS-oxidation. Afterwards the surface-bound diffused bitline was formed. Trenches were then opened and the trench-bottom bound bitlines were formed. Trench filling by a deposition / etchback process completed this module. 14 program etch step defined openings for vertical transistor formation at sites, were a "0" was intended to be stored The gateoxide was grown simultaneously for the CMOSperiphery and the vertical transistors. In order to prevent any segregation driven depletion of the p-well dopant concent...

We present the experimental demonstration of light storage towards the single photon level at a long storage time by electromagnetically induced transparency in a rare-earth ion-doped Pr3+:Y2SiO5 crystal. We apply decoherence control by static magnetic fields and appropriately designed radio-frequency composite pulse sequences to prolong the storage time in the memory. A rare-earth ion-doped filter crystal prepared by optical pumping serves to efficiently separate the signal at the single photon level from optical noise. Multipass setups around the memory and the filter crystal improve the storage efficiency and filter selectivity. Already without decoherence control, the setup permits storage of single photons in the microsecond regime at a storage efficiency of 42%. With decoherence control we demonstrate storage of weak coherent pulses containing some 10 photons for up to 10 s at a storage efficiency of several percent. The experimental data clearly demonstrate the applicability of EIT light storage to implement a true quantum memory in Pr3+:Y2SiO5 at long storage times. The scientific findings and technical developments are of relevance also to other protocols and media for quantum information storage.