Current undergraduate students
Exponential Separation between Quantum Communication Complexity and Classical Information Complexity
Dave Touchette, IQC
We exhibit a Boolean function for which the quantum communication complexity is exponentially larger than the classical information complexity. An exponential separation in the other direction was already known from the work of Kerenidis et. al. [SICOMP 44, pp. 1550--1572], hence our work implies that these two complexity measures are incomparable. As classical information complexity is an upper bound on quantum information complexity, which in turn is equal to amortized quantum communication complexity, our work implies that a tight direct sum result for distributional quantum communication complexity cannot hold.
Dicke's Superradiance in Astrophysics
Fereshteh Rajabi, University of Western Ontario
It is generally assumed that in the interstellar medium much of the emission emanating from atomic and molecular transitions within a radiating gas happen independently for each atom or molecule, but as was pointed out by R. H. Dicke in a seminal paper several decades ago this assumption does not apply in all conditions. As will be discussed in my presentation, and following Dicke's original analysis, closely packed atoms/molecules can interact with their common electromagnetic field and radiate coherently through an effect he named superradiance.
Efficient Quantum Algorithms for Simulating Lindblad Evolution
Chunhao Wang
The Lindblad equation is the natural generalization to open systems of the Schrödinger equation. We give a quantum algorithm for simulating the evolution of an n-qubit system under the Lindblad equation with local terms. The gate cost of the algorithm is O(mTlog^2(T/\epsilon)/loglog(T/\epsilon)), where T is the evolution time, \epsilon is the precision of the output state, and m is the number of local terms occurring in the equation.
Graphs and Multi-mode Coupling: How to build a programmable, directional parametric amplifier
Jose Aumentado, National Institute of Standards and Technology, Boulder
Parametric amplification is a big deal these days, especially for research in superconducting quantum information. This is because, in principle, parametric amplifiers can amplify a signal while adding the minimum amount of noise that quantum mechanics allows. In practice, the situation is a little more complicated and the practical measurement chains can degrade this ideal performance.
Cybersecurity is Hard. Up for a Challenge?
Mark McArdle, eSentire
Pure technology approaches to cybersecurity consistently fail to prevent hackers from breaching networks and systems. The pursuit of a pure technology solution to cybersecurity is going to require significant breakthroughs in AI and machine learning. Come join a discussion about why cybersecurity is such a hard problem and review some promising areas of research that may bring positive changes.
Generation and Spectral Characterization of High-Purity Biphotons
Franco Wong, Massachusetts Institute of Technology
Spectrally factorable biphotons are highly desirable for many photonic quantum information processing tasks such as quantum computation, boson sampling, and quantum repeaters. We generate biphotons with spectral purity of 99%, the highest to date without any spectral filtering, by pulsed spontaneous parametric downconversion in a custom-fabricated PPKTP crystal under extended Gaussian phase-matching conditions.
Entanglement and Purcell Effects in Systems for Quantum Information and Sensing
Stephen K. Gray, Argonne National Laboratory
I discuss how to propagate the quantum mechanical density matrix, including dephasing, spontaneous emission and dissipation for systems relevant to quantum information and sensing. Two applications are then presented. In the first example, a plasmonic system is coupled to quantum dots. The plasmonic system could be a single metal nanoparticle or an array of metal nanoparticles and can be viewed as an optical resonator.
SIC-POVMs and algebraic number theory
John Yard, Institute for Quantum Computing
SIC-POVMs (Symmetric Informationally Complete Positive Operator-Valued Measures) are certain extremal rank-1 projective measurements corresponding to maximal sets of complex equiangular lines as well as to minimal complex projective 2-designs. They are conjectured to exist in every finite-dimensional complex Hilbert space as orbits of generalized Pauli groups.
Contextuality as a resource for quantum computation
Juan Bermejo Vega
A central question in quantum computation is to identify the resources that are responsible for quantum speed-up. Quantum contextuality has been recently shown to be a resource for quantum computation with magic states for odd-prime dimensional qudits and two-dimensional systems with real wavefunctions. The phenomenon of state-independent contextuality poses a priori an obstruction to characterizing the case of regular qubits, the fundamental building block of quantum computation.
A proof of the quantum data processing inequality with a combinatorial flavour
Ashwin Nayak, Institute for Quantum Computing
The quantum data processing inequality (equivalently, the strong sub-additivity of von Neumann entropy) is a cornerstone of quantum information theory. It has been proven in numerous ways, each proof highlighting different aspects of the property.