6,086 research outputs found
Optimizing Quantum Programs against Decoherence: Delaying Qubits into Quantum Superposition
Quantum computing technology has reached a second renaissance in the last
decade. However, in the NISQ era pointed out by John Preskill in 2018, quantum
noise and decoherence, which affect the accuracy and execution effect of
quantum programs, cannot be ignored and corrected by the near future NISQ
computers. In order to let users more easily write quantum programs, the
compiler and runtime system should consider underlying quantum hardware
features such as decoherence. To address the challenges posed by decoherence,
in this paper, we propose and prototype QLifeReducer to minimize the qubit
lifetime in the input OpenQASM program by delaying qubits into quantum
superposition. QLifeReducer includes three core modules, i.e.,the parser,
parallelism analyzer and transformer. It introduces the layered bundle format
to express the quantum program, where a set of parallelizable quantum
operations is packaged into a bundle. We evaluate quantum programs before and
after transformed by QLifeReducer on both real IBM Q 5 Tenerife and the
self-developed simulator. The experimental results show that QLifeReducer
reduces the error rate of a quantum program when executed on IBMQ 5 Tenerife by
11%; and can reduce the longest qubit lifetime as well as average qubit
lifetime by more than 20% on most quantum workloads.Comment: To appear in TASE2019 - the 13th International Symposium on
Theoretical Aspects of Software Engineering (submitted on Jan 25, 2019, and
this is camera-ready version
Photon scattering by an atomic ensemble coupled to a one-dimensional nanophotonic waveguide
We theoretically investigate the quantum scattering of a single-photon pulse
interacting with an ensemble of -type three-level atoms coupled to a
one-dimensional waveguide. With an effective non-Hermitian Hamiltonian, we
study the collective interaction between the atoms mediated by the waveguide
mode. In our scheme, the atoms are randomly placed in the lattice along the
axis of the one-dimensional waveguide, which closely corresponds to the
practical condition that the atomic positions can not be controlled precisely
in experiment. Many interesting optical properties occur in our waveguide-atom
system, such as electromagnetically induced transparency (EIT) and optical
depth. Moreover, we observe that strong photon-photon correlation with quantum
beats can be generated in the off-resonant case, which provides an effective
candidate for producing non-classical light in experiment. With remarkable
progress in waveguide-emitter system, our scheme may be feasible in the near
future.Comment: 10 pages,7 figure
A Review of Recent Advances in Red-Clay Environmental Magnetism and Paleoclimate History of the Chinese Loess Plateau
The red-clay sequence on the Chinese Loess Plateau (CLP) was deposited during the late Miocene-Pliocene and is encoded with important information of past climate changes. However, it has received much less study in comparison to the overlying Pleistocene loess-paleosol sequence. In this paper, we review recent progress in characterizing the environmental magnetic parameter-based paleoclimate history recorded by the red-clay sequence. Several key conclusions are as follows. (1) the red-clay and the loess-paleosol sequences have similar magnetic enhancement mechanisms but magnetic minerals in the red-clay sequence have experienced a higher degree of oxidation than in the loess-paleosol sequence. (2) The CLP experienced a cooling and wetting trend from 4.5 to 2.7 Ma, caused by ice sheet expansion and East Asian summer monsoon intensification, respectively. (3) The above conclusions benefit from backfield remanence curve unmixing and comparison of magnetic grain size/concentration records, which are particularly useful in separating the temperature from the precipitation signal. A clear need in future studies is to explore the concentration and the grain size variations of hematite and goethite in the red-clay sequence and their formation mechanisms. The payback would be a clear understanding of climate history during the late Miocene-Pliocene, a possible analog for future warmer climate
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