Group-blind detection with very large antenna arrays in the presence of pilot contamination

Massive MIMO is, in general, severely affected by pilot contamination. As opposed to traditional detectors, we propose a group-blind detector that takes into account the presence of pilot contamination. While sticking to the traditional structure of the training phase, where orthogonal pilot sequences are reused, we use the excess antennas at each base station to partially remove interference during the uplink data transmission phase. We analytically derive the asymptotic SINR achievable with group-blind detection, and confirm our findings by simulations. We show, in particular, that in an interference-limited scenario with one dominant interfering cell, the SINR can be doubled compared to non-group-blind detection.Comment: 5 pages, 4 figure

Imaging-based Parametric Resonance in an Optical Dipole Atom Trap

We report sensitive detection of parametric resonances in a high-density sample of ultracold $^{87}Rb$ atoms confined to a far-off-resonance optical dipole trap. Fluorescence imaging of the expanded ultracold atom cloud after a period of parametric excitation shows significant modification of the atomic spatial distribution and has high sensitivity compared with traditional measurements of parametrically-driven trap loss. Using this approach, a significant shift of the parametric resonance frequency is observed, and attributed to the anharmonic shape of the dipole trap potential

Structured Near-Optimal Channel-Adapted Quantum Error Correction

We present a class of numerical algorithms which adapt a quantum error correction scheme to a channel model. Given an encoding and a channel model, it was previously shown that the quantum operation that maximizes the average entanglement fidelity may be calculated by a semidefinite program (SDP), which is a convex optimization. While optimal, this recovery operation is computationally difficult for long codes. Furthermore, the optimal recovery operation has no structure beyond the completely positive trace preserving (CPTP) constraint. We derive methods to generate structured channel-adapted error recovery operations. Specifically, each recovery operation begins with a projective error syndrome measurement. The algorithms to compute the structured recovery operations are more scalable than the SDP and yield recovery operations with an intuitive physical form. Using Lagrange duality, we derive performance bounds to certify near-optimality.Comment: 18 pages, 13 figures Update: typos corrected in Appendi

Optical Manipulation of Light Scattering in Cold Atomic Rubidium

A brief perspective on light scattering in dense and cold atomic rubidium is presented. We particularly focus on the influence of auxiliary applied fields on the system response to a weak and nearly resonant probe field. Auxiliary fields can strongly disturb light propagation; in addition to the steady state case, dynamically interesting effects appear clearly in both the time domain, and in the optical polarization dependence of the processes. Following a general introduction, two examples of features found in such studies are presented. These include nonlinear optical effects in (a) comparative studies of forward- and fluorescence-configuration scattering under combined excitation of a control and probe field, and (b) manipulation of the spatial structure of the optical response due to a light shifting strong applied field

Human Rights Protection for Indonesian Migrant Workers: Challenges for ASEAN

The AEC is good news for Indonesian migrant workers wanting to work overseas. Unfortunately, many Indonesian migrant workers have been deported from ASEAN countries because of having problems. This study adopts the normative legal research method. It argues that AICHR may be slow in resolving the problems of human rights. It is also argued that the ASEAN Committee on Migrant Workers works in the absence of the political commitment of ASEAN leaders to implement the Cebu Declaration. Therefore, the best solution is public participation in the ASEAN countries to protect migrant workers.IntisariKomunitas Masyarakat Ekonomi ASEAN adalah berita baik untuk Tenaga Kerja Indonesia (TKI) untuk bekerja di luar negeri. Namun, banyak TKI yang kembali dari negara-negara ASEAN dikarenakan mendapatkan berbagai permasalahan. Penelitian ini mengadopsi jenis penelitian hukum normatif. Penelitian ini menyimpulkan bahwa AICHR lamban dalam menyelesaikan permaslahan tentang hak asasi manusia. Penelitian ini juga menyimpulkan bahwa komunitas ASEAN tentang Pekerja Migran bekerja dengan tidak adanya komitmen politik dari para pemimpim ASEAN dalam menerapkan Deklarasi Cebu. Oleh sebab itu, dibutuhkan partisipasi ASEAN dalam melindungi TKI

Optimum Quantum Error Recovery using Semidefinite Programming

Quantum error correction (QEC) is an essential element of physical quantum information processing systems. Most QEC efforts focus on extending classical error correction schemes to the quantum regime. The input to a noisy system is embedded in a coded subspace, and error recovery is performed via an operation designed to perfectly correct for a set of errors, presumably a large subset of the physical noise process. In this paper, we examine the choice of recovery operation. Rather than seeking perfect correction on a subset of errors, we seek a recovery operation to maximize the entanglement fidelity for a given input state and noise model. In this way, the recovery operation is optimum for the given encoding and noise process. This optimization is shown to be calculable via a semidefinite program (SDP), a well-established form of convex optimization with efficient algorithms for its solution. The error recovery operation may also be interpreted as a combining operation following a quantum spreading channel, thus providing a quantum analogy to the classical diversity combining operation.Comment: 7 pages, 3 figure

Channel-Adapted Quantum Error Correction

Abstract—Error correction procedures are considered which are designed specifically for the amplitude damping channel. Amplitude damping errors are analyzed in the stabilizer formalism. This analysis allows a generalization of the [4; 1] “approximate ” amplitude damping code. This generalization is presented as a class of [2(M +1);M] codes; quantum circuits for encoding and recovery operations are presented. A [7; 3] amplitude damping code based on the classical Hamming code is presented. All of these are stabilizer codes whose encoding and recovery operations can be completely described with Clifford group operations. Finally, optimization options are described in which recovery operations may be further adapted according to the damping probability. Index Terms—Amplitude damping channel, quantum error correction, stabilizer codes. I