APS March Meeting Student Practice Talk Session
Shazhou (Joey) Zhong: Dimensionality-tuned semimetal-to-metal transition in 1Td-MoTe2
We study magnetotransport in 1Td-MoTe2 ultrathin flakes at low temperature. The samples are fabricated by mechanical exfoliation and capped with hBN to protect from oxidation. In contrast to bulk crystals, which show large magnetoresistance due to near-perfect electron-hole compensation, we find greater charge imbalance with reduced thickness. The results may explain stabilization of the orthorhombic phase in ultrathin samples as found by He et al.
Chung Wai Sandbo Chang: Observation of genuine three-mode interference produced by higher order spontaneous parametric downconversion
Parametric processes are well recognized as key elements for various quantum protocols. Advancing to higher-order parametric processes has been an on-going challenge. In particular, a long-sought goal in quantum optics has been third-order spontaneous parametric down-conversion (SPDC), where photons are directly created in triplets. We report the generation of microwave signals from third-order SPDC in a multimode parametric cavity when pumping both a single mode and three coupled modes. By pumping at the triple frequency of a single mode, we observe a phase-space distribution with a non-Gaussian profile which shows strong skewness in the quadrature amplitude distribution. By pumping at the sum frequency of three modes, we observe non-zero coskewness between the quadrature amplitudes of the modes. These phase-dependent three-mode correlations are observed even though the two-mode covariance between any two of the three modes is zero. This suggest the existence of a nontrivial three-mode continuous variable interference. These types of non-Gaussian states have been suggested as a resource enabling universal quantum computation with continuous variables. The multimode states may also be useful for three-party quantum communication protocols such as quantum secret sharing.
Nayeli Azucena Rodriguez-Briones: Correlation-Enhanced Algorithmic Cooling
The field of quantum information has inspired new methods for cooling physical systems at the quantum scale. In particular, heat-bath algorithmic cooling (HBAC) methods operate by manipulating entropy at the quantum level and making contact with a bath. These techniques are at the core of practical applications of quantum information science: in quantum computing, they provide a controlled way to prepare highly pure quantum states (which are required from the state initialization of most quantum algorithms to a reliable supply of ancilla qubits that satisfy the fault-tolerance threshold for quantum error correction). In this talk, we generalize HBAC methods to allow the presence of correlations due to internal interaction-- and we show that these correlations provide a resource that can be used to improve cooling beyond previously established limits. Furthermore, we show that correlated relaxation processes between the system and environment during rethermalization can be also exploited to enhance purification.
*This work was supported by CONACYT, the Mike and Ophelia Lazaridis Fellowship program, Industry Canada and the government of Ontario, CIFAR, and U.S. Army Research Laboratory.
Tarun Patel: Photocurrent imaging of charge density wave transitions in ultrathin 1T-TaS2
We use scanning photocurrent microscopy to image the nearly commensurate/commensurate charge density wave transition in 1T-TaS2. Ultrathin flakes are fabricated by mechanical exfoliation and protected from oxidation with h-BN capping in an inert atmosphere. We study the effect of dimensionality and in-plane current on the first-order phase transition with spatial resolution within the diffraction limit.
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