413 research outputs found
Milton R. Konvitz: A Bibliography
Milton Konvitz (Ph.D. \u2733) embodied the spirit of Cornell University. An authority on civil rights and human rights, and constitutional and labor law, he served on the Cornell faculty for 27 years, holding dual appointments at the Law School and the School of Industrial and Labor Relations. This section features a bibliography by Phillip R. Dankert, Collection Development Librarian, Martin P. Catherwood Library, Cornell University
Exact and Approximate Unitary 2-Designs: Constructions and Applications
We consider an extension of the concept of spherical t-designs to the unitary group in order to develop a unified framework for analyzing the resource requirements of randomized quantum algorithms. We show that certain protocols based on twirling require a unitary 2-design. We describe an efficient construction for an exact unitary 2-design based on the Clifford group, and then develop a method for generating an epsilon-approximate unitary 2-design that requires only O(n log(1/epsilon)) gates, where n is the number of qubits and epsilon is an appropriate measure of precision. These results lead to a protocol with exponential resource savings over existing experimental methods for estimating the characteristic fidelities of physical quantum processes
Quantum non-malleability and authentication
In encryption, non-malleability is a highly desirable property: it ensures
that adversaries cannot manipulate the plaintext by acting on the ciphertext.
Ambainis, Bouda and Winter gave a definition of non-malleability for the
encryption of quantum data. In this work, we show that this definition is too
weak, as it allows adversaries to "inject" plaintexts of their choice into the
ciphertext. We give a new definition of quantum non-malleability which resolves
this problem. Our definition is expressed in terms of entropic quantities,
considers stronger adversaries, and does not assume secrecy. Rather, we prove
that quantum non-malleability implies secrecy; this is in stark contrast to the
classical setting, where the two properties are completely independent. For
unitary schemes, our notion of non-malleability is equivalent to encryption
with a two-design (and hence also to the definition of Ambainis et al.). Our
techniques also yield new results regarding the closely-related task of quantum
authentication. We show that "total authentication" (a notion recently proposed
by Garg, Yuen and Zhandry) can be satisfied with two-designs, a significant
improvement over the eight-design construction of Garg et al. We also show
that, under a mild adaptation of the rejection procedure, both total
authentication and our notion of non-malleability yield quantum authentication
as defined by Dupuis, Nielsen and Salvail.Comment: 20+13 pages, one figure. v2: published version plus extra material.
v3: references added and update
Randomized benchmarking of single and multi-qubit control in liquid-state NMR quantum information processing
Being able to quantify the level of coherent control in a proposed device
implementing a quantum information processor (QIP) is an important task for
both comparing different devices and assessing a device's prospects with
regards to achieving fault-tolerant quantum control. We implement in a
liquid-state nuclear magnetic resonance QIP the randomized benchmarking
protocol presented by Knill et al (PRA 77: 012307 (2008)). We report an error
per randomized pulse of with a
single qubit QIP and show an experimentally relevant error model where the
randomized benchmarking gives a signature fidelity decay which is not possible
to interpret as a single error per gate. We explore and experimentally
investigate multi-qubit extensions of this protocol and report an average error
rate for one and two qubit gates of for a three
qubit QIP. We estimate that these error rates are still not decoherence limited
and thus can be improved with modifications to the control hardware and
software.Comment: 10 pages, 6 figures, submitted versio
Swift C–C bond insertion by a 12-electron palladium(0) surrogate
The selective activation of C–C bonds holds vast promise for
catalysis. So far, research has been primarily directed at rhodium
and nickel under harsh reaction conditions. Herein, we report C–C
insertion reactions of a 12-electron palladium(0) surrogate stabilized by
a cyclic(alkyl)(amino) carbene (CAAC) ligand. Benzonitrile (1), biphenylene (2), benzocyclobutenone (3), and naphtho[b]cyclopropene (4) were
studied. These substrates allow elucidation of the effect of ring strain as
well as hybridization encompassing sp3
, sp2 and sp hybridized carbon
atoms. All reactions proceed quantitatively at or below room temperature. This work therefore outlines perspectives for mild C–C bond
functionalization catalysis
One-dimensional ferromagnetic edge contacts to two-dimensional graphene/h-BN heterostructures
We report the fabrication of one-dimensional (1D) ferromagnetic edge contacts
to two-dimensional (2D) graphene/h-BN heterostructures. While aiming to study
spin injection/detection with 1D edge contacts, a spurious magnetoresistance
signal was observed, which is found to originate from the local Hall effect in
graphene due to fringe fields from ferromagnetic edge contacts and in the
presence of charge current spreading in the nonlocal measurement configuration.
Such behavior has been confirmed by the absence of a Hanle signal and
gate-dependent magnetoresistance measurements that reveal a change in sign of
the signal for the electron- and hole-doped regimes, which is in contrast to
the expected behavior of the spin signal. Calculations show that the
contact-induced fringe fields are typically on the order of hundreds of mT, but
can be reduced below 100 mT with careful optimization of the contact geometry.
There may be additional contribution from magnetoresistance effects due to
tunneling anisotropy in the contacts, which need to be further investigated.
These studies are useful for optimization of spin injection and detection in 2D
material heterostructures through 1D edge contacts
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