This award to the Joint Quantum Institute (JQI) provides support to enable high-risk, speculative experimental and theoretical activity in the control and use of quantum coherence and entanglement - the basis of a second quantum revolution. The combination of Information Theory with Quantum Mechanics has created the new field of Quantum Information Science (QIS), which has the potential to revolutionize how information is processed and stored. Quantum coherence and quantum entanglement are universal to all quantum physical systems, in much the same sense that the processing of information is independent of the information's physical embodiment. Future success in propagating quantum coherence, preparing complex quantum entangled states, and managing decoherence will likely hinge upon the interconversion of quantum coherence among various physical platforms, for example: solid-state photon sources, individual ions, ultracold atomic gases in optical lattices, and superconducting devices.
The Physics Frontiers Center (PFC) at JQI will facilitate the integration of Atomic, Molecular and Optical (AMO) and Condensed Matter (CM) systems for the study of QIS through three major activities: (1) Correlated and Topological Matter with Cold Atoms will create and investigate topological and other novel forms of quantum-correlated matter in cold atomic and molecular systems. Using probes of single-particle properties and measures of quantum entanglement, this activity will provide insight into the emergence and dynamics of exotic phases in real or artificial condensed-matter systems. (2) Supercircuits at the AMO/CM Interface will bring together AMO and CM techniques and perspectives to treat "supercircuits": superconducting electrical circuits and mechanical circuits of atomic gas superfluids. A combination of AMO/CM couplings and AMO/CM analogies will provide new insights into supercircuits and superfluidity as well as develop new tools for quantum information. (3) Quantum Optics with Semiconductors and Atoms will investigate methods to transfer coherence and create entanglement between matter and light and to produce complex many-body entanglement in semiconductors and atomic systems.
The emergence of QIS has propelled a convergence of CM and AMO physics. Graduate students and post-doctoral associates supported through the PFC will be trained at that interface. A the high school level, the PFC will institute a program to enrich the teaching of physics and mathematics in Prince George's County (PG) high schools, including offering paid summer research internships to as many as six PG County Public School teachers. The teachers will work alongside scientists in PFC projects and will meet weekly with JQI fellows to discuss their summer experiences, current science topics, and issues they confront in their classrooms. The PFC will have an informative, educational, and topical web site, an active seminar series, a program of JQI travelling lecturers, and an annual open house. The PFC will support, maintain, and expand the Physics Lecture Demonstrations at UMD, and develop new channels to disseminate findings to both the scientific and non-technical communities.
Quantum mechanics revolutionized the physics and technology of the 20th century; it enabled our current information-intensive society. The Physics Frontier Center at the Joint Quantum Institute (PFC@JQI) is in the vanguard of a second quantum revolution, addressing quantum coherent phenomena at the interface of Atomic, Molecular and Optical (AMO) and Condensed Matter (CM) physics. Intellectual Merit: Studies of Topological Matter and Majorana Fermions Quantum materials are increasingly important for devices, quantum information, and fundamental physics. Our theorists showed how to combine two such materials: topological insulators and superconductors to achieve the elusive Majorana fermion (no elementary particle is known to be one). Following this theoretical design, external experimental groups have realized Majorana quasiparticles. Qubits made from these Majorana fermion quasiparticles should benefit from topological protection, and be more immune from decoherence than conventional qubits and thus may aid the advent of quantum computation. Topology offers this protection because it is a global aspect of the system, so local disruptions are ineffective. PFC@JQI theorists have also prediction of a so-called Topological Kondo insulating compound recently confirmed by three independent experimental groups. The PFC@JQI has also fostered research on realizing topological properties with cold atoms and photonic devices, where different opportunities for control and measurement should produce new insights and research directions. Synthetic Gauge Fields and Spin-orbit Coupling Synthetic magnetic and electric fields for neutral atomic gases offer a new toolbox for simulating fundamentally important quantum systems. Our experimentalists pioneered the use of laser light to create such fields for neutral atoms. The atoms behave as if they are charged particles interacting with a field even though none is present and the atoms have no charge. This achievement opens new avenues of many-body research that were barely imaginable before. The synthetic magnetic field cause quantized vortices of circulation to enter the BEC, just as applying a magnetic field to a conducting fluid would induce circulating current tending to cancel out the applied field. Motivated by our CM theorists, the experimentalists used the same laser fields that produce synthetic vector potentials to create spin-orbit coupling for the atoms. Spin-orbit coupling links the velocity of a particle to its quantum-mechanical spin, and is essential to important CM phenomena, including topological insulators and Majorana fermions. In solid materials, spin-orbit coupling originates from movement of electrons in intrinsic electric fields of the crystal and varies for different materials. In contrast, for ultracold atoms, we can engineer tunable material parameters with chosen properties. Quantum Simulation with Ion Chains: Our experimentalists, in collaboration with theorists, utilize chains of atomic ions combined with laser fields to simulate quantum systems, with the hope of shedding light on complex, otherwise intractable CM and quantum phenomena. Entanglement, which is a type of correlation that distinguishes purely quantum systems from classical ones, can arise from interactions between particles. In one quantum simulation, our team has examined how quickly quantum connections formed in an ion crystal. This system is described by some "spin" models, which are mathematical representations of a number of phenomena, including magnetism. The ultimate limit, in both classical and quantum systems, is given by the speed of light. However, decades ago, physicists showed that a slower information speed limit emerges due to spin-spin interactions, similar to sound propagation in mechanical systems. Indeed, the experiment shows that long-range interactions provide a comparative speed-up for sending information across the ion-spin crystal. Scaling up this study may have profound implications for our understanding of quantum systems more generally. For example, the growth of entanglement, which is a form of information that must obey the bounds described above, is intimately related to the difficulty of modeling quantum systems on a computer. For system sizes not much larger than those found in these experiments, modeling becomes impossible for a conventional computer. Broader Impacts: The PFC@JQI has enabled the students to break down barriers between the AMO and CM. They are learning one another's languages and are giving birth to a new, common language. During each year of grant we have supported at least 17 graduate students, many of whom have gone to jobs in national laboratories, industry, postdoctoral work, and academic positions. Our international collaborations continue at all levels, from graduate and postdoctoral exchanges to professors. The weekly seminar at the JQI attracts more than 100 participants. It presents topics on both CM and AMO. The PFC@JQI has organized or taken part in workshops and national and international conferences. Our Outreach includes support for the Summer Girls, an intensive, hands-on program that brings upcoming 9th- and 11th-graders to UMD for two weeks of physics instruction, exploration and experiment. We visit local K-12 schools and colleges in the DC metropolitan area to present and promote quantum physics. We have been developing quantum science demonstrations and participate in the USA Science and Engineering Festival held in DC.
