- University of Massachusetts Boston
- https://www.sunclipse.org
- Joined 30 May 2014

- In three very recent papers, (an initial paper by Morishima and Futamase, and two subsequent papers by Morishima, Futamase, and Shimizu), it has been argued that the observed experimental anomaly in the anomalous magnetic moment of the muon might be explained using general relativity. It is my melancholy duty to report that these articles are fundamentally flawed in that they fail to correctly implement the Einstein equivalence principle of general relativity. Insofar as one accepts the underlying logic behind these calculations (and so rejects general relativity) the claimed effect due to the Earth's gravity will be swamped by the effect due to Sun (by a factor of fifteen), and by the effect due to the Galaxy (by a factor of two thousand). In contrast, insofar as one accepts general relativity, then the claimed effect will be suppressed by an extra factor of [(size of laboratory)/(radius of Earth)]^2. Either way, the claimed effect is not compatible with explaining the observed experimental anomaly in the anomalous magnetic moment of the muon.
- Identifying the property of the world that enforces the Born rule is a longstanding problem in physics. We prove that in any physical theory that assigns probabilities to the outcomes of ideal measurements, the maximal set of probability assignments for each graph of exclusivity is the one that satisfies the Born rule. Therefore, the agreement between quantum theory and experiments follows from a one-to-one correspondence between the logical possibilities and the physical possibilities and, in particular, implies that the outcomes of quantum measurements are not constrained by any physical reason.
- Jan 18 2018 quant-ph arXiv:1801.05798v2There is an ongoing search for intuitive postulates of quantum theory from which its Hilbert space structure can be derived. The main contribution of this paper is the introduction of two postulates inspired by categorical logical notions from effectus theory, a framework in some ways similar to generalised probabilistic theories, but eschewing the familiar notions of real numbers and probabilities, which allows the description of more general theories. The postulates state the existence of certain physical filters that associate to each effect the subspace where it holds true. We show that when considering an operational probabilistic setting these relatively weak postulates lead to a spectral theorem and a duality between pure states and effects: each effect can be written as a probabilistic combination of perfectly distinguishable sharp effects in a unique way. In such a weak theory it is therefore already possible to define thermodynamic quantities like entropy. For these results we don't need any assumptions on the existence of pure states, or of sufficiently many reversible dynamics or even the existence of an invariant state. We finish the reconstruction of quantum theory by requiring three additional postulates: continuous symmetry, preservation of purity, and observability of energy.
- Jan 16 2018 quant-ph arXiv:1801.04795v1Permutational Quantum Computing (Jordan, 2009) is a natural quantum computational model that was conjectured to capture non-classical aspects of quantum computation. Contrary to the previous conjecture, we find a classical algorithm that efficiently approximates output distributions of the model up to polynomially small additive precision. We extend this algorithm to show that a large class of important quantum circuits - the Quantum Schur Sampling circuits - can be also efficiently simulated classically. The algorithm can be used to efficiently estimate non-trivial elements of irreducible representation matrices of the symmetric group on $n$ elements and might be also used to approximate transition amplitudes of the Ponzano-Regge model.
- Most works on adversarial examples for deep-learning based image classifiers use noise that, while small, covers the entire image. We explore the case where the noise is allowed to be visible but confined to a small, localized patch of the image, without covering any of the main object(s) in the image. We show that it is possible to generate localized adversarial noises that cover only 2% of the pixels in the image, none of them over the main object, and that are transferable across images and locations, and successfully fool a state-of-the-art Inception v3 model with very high success rates.
- Jan 16 2018 quant-ph arXiv:1801.04807v2Two primary facets of quantum technological advancement that hold great promise are quantum communication and quantum computation. For quantum communication, the canonical resource is entanglement. For quantum gate implementation, the resource is 'magic' in an auxiliary system. It has already been shown that quantum coherence is the fundamental resource for the creation of entanglement. We argue on the similar spirit that quantum coherence is the fundamental resource when it comes to the creation of magic. This unifies the two strands of modern development in quantum technology under the common underpinning of existence of quantum superposition, quantified by the coherence in quantum theory. We also attempt to obtain magic monotones inspired from coherence monotones and vice versa. We further study the interplay between quantum coherence and magic in a qutrit system and that between quantum entanglement and magic in a qutrit-qubit setting.
- We consider the problem of stability of anti-de Sitter spacetime in five dimensions under small purely gravitational perturbations satisfying the cohomogeneity-two biaxial Bianchi IX ansatz. In analogy to spherically symmetric scalar perturbations, we observe numerically a black hole formation on the time-scale $\mathcal{O}(\varepsilon^{-2})$, where $\varepsilon$ is the size of the perturbation.
- In this review, we retrace the recent progress in the anti-de Sitter (AdS) instability problem. By instability we mean that for large classes of initial data, any perturbation of AdS space-time, however small, leads to the formation of a black hole. Since the seminal work of Bizoń and Rostworowski in 2011, many different kinds of numerical experiments were performed in asymptotically AdS space-times, unveiling a very intricate structure of the instability. In particular, many efforts were dedicated to the search of islands of stability, i.e.\ families of initial data that resist black hole formation. Many analytical and numerical tools were deployed to disentangle stable from unstable initial data, and shed new light on the necessary and sufficient conditions for collapse. Recently, research beyond spherical symmetry became more and more engaged. This is a very promising channel of investigation toward a deeper understanding of the gravitational dynamics in asymptotically AdS space-times.
- Nov 23 2017 quant-ph arXiv:1711.08066v1Contextuality is a necessary resource for universal quantum computation and non-contextual quantum mechanics can be simulated efficiently by classical computers in many cases. Orders of Planck's constant, $\hbar$, can also be used to characterize the classical-quantum divide by expanding quantities of interest in powers of $\hbar$---all orders higher than $\hbar^0$ can be interpreted as quantum corrections to the order $\hbar^0$ term. We show that contextual measurements in finite-dimensional systems have formulations within the Wigner-Weyl-Moyal (WWM) formalism that require higher than order $\hbar^0$ terms to be included in order to violate the classical bounds on their expectation values. As a result, we show that contextuality as a resource is equivalent to orders of $\hbar$ as a resource within the WWM formalism. This explains why qubits can only exhibit state-independent contextuality under Pauli observables as in the Peres-Mermin square while odd-dimensional qudits can also exhibit state-dependent contextuality. In particular, we find that qubit Pauli observables lack an order $\hbar^0$ contribution in their Weyl symbol and so exhibit contextuality regardless of the state being measured. On the other hand, odd-dimensional qudit observables generally possess non-zero order $\hbar^0$ terms, and higher, in their WWM formulation, and so exhibit contextuality depending on the state measured: odd-dimensional qudit states that exhibit measurement contextuality have an order $\hbar^1$ contribution that allows for the violation of classical bounds while states that do not exhibit measurement contextuality have insufficiently large order $\hbar^1$ contributions.
- Speech on the occasion of accepting the Dagmar and Vaclav Havel Foundation VIZE 97 Prize for 2017. Delivered at Prague Crossroads, October 5, 2017

- Supported by Silverpond.