Dipole blockade without dipole-dipole interaction

The dipole blockade phenomenon is a direct consequence of strong dipole-dipole interaction, where only single atom can be excited because the doubly excited state is shifted out of resonance. The corresponding two-body entanglement with non-zero concurrence induced by the dipole blockade effect is an important resource for quantum information processing. Here, we propose a novel physical mechanism for realizing dipole blockade without the dipole-dipole interaction, where two qubits coupled to a cavity, are driven by a coherent field. By suitably chosen placements of the qubits in the cavity and by adjusting the relative decay strengths of the qubits and cavity field, we kill many unwanted excitation pathways. This leads to dipole blockade. In addition, we show that these two qubits are strongly entangled over a broad regime of the system parameters. We show that a strong signature of this dipole blockade is the bunching property of the cavity photons which thus provides a possible measurement of the dipole blockade. We present dynamical features of the dipole blockade without dipole-dipole interaction. The proposal presented in this work can be realized not only in traditional cavity QED, but also in non-cavity topological photonics involving edge modes

Light, the universe, and everything -- 12 Herculean tasks for quantum cowboys and black diamond skiers

The Winter Colloquium on the Physics of Quantum Electronics (PQE) has been a seminal force in quantum optics and related areas since 1971. It is rather mindboggling to recognize how the concepts presented at these conferences have transformed scientific understanding and human society. In January, 2017, the participants of PQE were asked to consider the equally important prospects for the future, and to formulate a set of questions representing some of the greatest aspirations in this broad field. The result is this multi-authored paper, in which many of the world's leading experts address the following fundamental questions: (1) What is the future of gravitational wave astronomy? (2) Are there new quantum phases of matter away from equilibrium that can be found and exploited - such as the time crystal? (3) Quantum theory in uncharted territory: What can we learn? (4) What are the ultimate limits for laser photon energies? (5) What are the ultimate limits to temporal, spatial, and optical resolution? (6) What novel roles will atoms play in technology? (7) What applications lie ahead for nitrogen-vacancy centers in diamond? (8) What is the future of quantum coherence, squeezing, and entanglement for enhanced superresolution and sensing? (9) How can we solve (some of) humanity's biggest problems through new quantum technologies? (10) What new understanding of materials and biological molecules will result from their dynamical characterization with free electron lasers? (11) What new technologies and fundamental discoveries might quantum optics achieve by the end of this century? (12) What novel topological structures can be created and employed in quantum optics