Philip Taranto

Department of Physics, School of Science,

University of Tokyo,

Japan

Hi there 👋 I’m Philip Taranto, JSPS post-doctoral fellow hosted by the group of Prof. Mio Murao at the University of Tokyo.

My main research interests lie at the interface of quantum physics, mathematics, and information science, focusing on fields including (but not limited to): quantum information theory, open quantum dynamics, quantum thermodynamics, quantum foundations, correlations & entanglement, stochastic & complex processes, quantum computation & simulation, and philosophy of physics & science.

All of my scientific articles are freely available on arXiv and some statistics regarding them can be found on Google Scholar.

Feel free to contact via email: philipguy.taranto@phys.s.u-tokyo.ac.jp.

selected publications

Efficiently Cooling Quantum Systems with Finite Resources: Insights from Thermodynamic Geometry

Philip Taranto, Patryk Lipka-Bartosik, Nayeli A. Rodríguez-Briones, Martí Perarnau-Llobet, Nicolai Friis, Marcus Huber, and Pharnam Bakhshinezhad

2024

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Landauer’s universal limit on heat dissipation during information erasure becomes increasingly crucial as computing devices shrink: minimising heat-induced errors demands optimal pure-state preparation. For this, however, Nernst’s third law posits an infinite-resource requirement: either energy, time, or control complexity must diverge. Here, we address the practical challenge of efficiently cooling quantum systems using finite resources. We investigate the ensuing resource trade-offs and present efficient protocols for finite distinct energy gaps in settings pertaining to coherent or incoherent control, corresponding to quantum batteries and heat engines, respectively. Expressing energy bounds through thermodynamic length, our findings illuminate the optimal distribution of energy gaps, detailing the resource limitations of preparing pure states in practical settings.
@misc{arXiv:2404.06649, title = {{Efficiently Cooling Quantum Systems with Finite Resources: Insights from Thermodynamic Geometry}}, author = {Taranto, Philip and Lipka-Bartosik, Patryk and Rodr{\' i}guez-Briones, Nayeli A. and Perarnau-Llobet, Mart{\' i} and Friis, Nicolai and Huber, Marcus and Bakhshinezhad, Pharnam}, year = {2024}, archiveprefix = {arXiv}, eprint = {2404.06649}, }
Hidden Quantum Memory: Is Memory There When Somebody Looks?

Philip Taranto, Thomas J. Elliott, and Simon Milz

Quantum, 2023

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In classical physics, memoryless dynamics and Markovian statistics are one and the same. This is not true for quantum dynamics, first and foremost because quantum measurements are invasive. Going beyond measurement invasiveness, here we derive a novel distinction between classical and quantum processes, namely the possibility of hidden quantum memory. While Markovian statistics of classical processes can always be reproduced by a memoryless dynamical model, our main result shows that this is not true in quantum mechanics: We first provide an example of quantum non-Markovianity whose manifestation depends on whether or not a previous measurement is performed – an impossible phenomenon for memoryless dynamics; we then strengthen this result by demonstrating statistics that are Markovian independent of how they are probed, but are nonetheless still incompatible with memoryless quantum dynamics. Thus, we establish the existence of Markovian statistics gathered by probing a quantum process that nevertheless fundamentally require memory for their creation.
@article{q-2023-04-27-991, title = {{Hidden Quantum Memory: Is Memory There When Somebody Looks?}}, author = {Taranto, Philip and Elliott, Thomas J. and Milz, Simon}, journal = {Quantum}, year = {2023}, volume = {7}, pages = {991}, doi = {10.22331/q-2023-04-27-991}, url = {https://doi.org/10.22331/q-2023-04-27-991}, archiveprefix = {arXiv}, eprint = {2204.08298}, }
Landauer Versus Nernst: What is the True Cost of Cooling a Quantum System?

Philip Taranto, Faraj Bakhshinezhad, Andreas Bluhm, Ralph Silva, Nicolai Friis, Maximilian P.E. Lock, Giuseppe Vitagliano, Felix C. Binder, Tiago Debarba, Emanuel Schwarzhans, Fabien Clivaz, and Marcus Huber

PRX Quantum, 2023

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Thermodynamics connects our knowledge of the world to our capability to manipulate and thus to control it. This crucial role of control is exemplified by the third law of thermodynamics, Nernst’s unattainability principle, which states that infinite resources are required to cool a system to absolute zero temperature. But what are these resources and how should they be utilized? And how does this relate to Landauer’s principle that famously connects information and thermodynamics? We answer these questions by providing a framework for identifying the resources that enable the creation of pure quantum states. We show that perfect cooling is possible with Landauer energy cost given infinite time or control complexity. However, such optimal protocols require complex unitaries generated by an external work source. Restricting to unitaries that can be run solely via a heat engine, we derive a novel Carnot-Landauer limit, along with protocols for its saturation. This generalizes Landauer’s principle to a fully thermodynamic setting, leading to a unification with the third law and emphasizes the importance of control in quantum thermodynamics.
@article{PRXQuantum.4.010332, title = {Landauer Versus Nernst: What is the True Cost of Cooling a Quantum System?}, author = {Taranto, Philip and Bakhshinezhad, Faraj and Bluhm, Andreas and Silva, Ralph and Friis, Nicolai and Lock, Maximilian P.E. and Vitagliano, Giuseppe and Binder, Felix C. and Debarba, Tiago and Schwarzhans, Emanuel and Clivaz, Fabien and Huber, Marcus}, journal = {PRX Quantum}, volume = {4}, issue = {1}, pages = {010332}, numpages = {61}, year = {2023}, publisher = {American Physical Society}, doi = {10.1103/PRXQuantum.4.010332}, url = {https://link.aps.org/doi/10.1103/PRXQuantum.4.010332}, }
When Is a Non-Markovian Quantum Process Classical?

Simon Milz, Dario Egloff, Philip Taranto, Thomas Theurer, Martin B. Plenio, Andrea Smirne, and Susana F. Huelga

Phys. Rev. X, 2020

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More than a century after the inception of quantum theory, the question of which traits and phenomena are fundamentally quantum remains under debate. Here, we give an answer to this question for temporal processes that are probed sequentially by means of projective measurements of the same observable. Defining classical processes as those that can, in principle, be simulated by means of classical resources only, we fully characterize the set of such processes. Based on this characterization, we show that for non-Markovian processes (i.e., processes with memory), the absence of coherence does not guarantee the classicality of observed phenomena; furthermore, we derive an experimentally and computationally accessible measure for nonclassicality in the presence of memory. We then provide a direct connection between classicality and the vanishing of quantum discord between the evolving system and its environment. Finally, we demonstrate that—in contrast to the memoryless setting—in the non-Markovian case, there exist processes that are genuinely quantum; i.e., they display nonclassical statistics independent of the measurement scheme that is employed to probe them.
@article{PhysRevX.10.041049, title = {{When Is a Non-Markovian Quantum Process Classical?}}, author = {Milz, Simon and Egloff, Dario and Taranto, Philip and Theurer, Thomas and Plenio, Martin B. and Smirne, Andrea and Huelga, Susana F.}, journal = {Phys. Rev. X}, volume = {10}, pages = {041049}, year = {2020}, doi = {10.1103/PhysRevX.10.041049}, archiveprefix = {arXiv}, eprint = {1907.05807}, }
Quantum Markov Order

Philip Taranto, Felix A. Pollock, Simon Milz, Marco Tomamichel, and Kavan Modi

Phys. Rev. Lett., 2019

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We formally extend the notion of Markov order to open quantum processes by accounting for the instruments used to probe the system of interest at different times. Our description recovers the classical property in the appropriate limit: when the stochastic process is classical and the instruments are noninvasive, i.e., restricted to orthogonal, projective measurements. We then prove that there do not exist non-Markovian quantum processes that have finite Markov order with respect to all possible instruments; the same process exhibits distinct memory effects when probed by different instruments. This naturally leads to a relaxed definition of quantum Markov order with respect to specified instrument sequences. The memory effects captured by different choices of instruments vary dramatically, providing a rich landscape for future exploration.
@article{PhysRevLett.122.140401, title = {{Quantum Markov Order}}, author = {Taranto, Philip and Pollock, Felix A. and Milz, Simon and Tomamichel, Marco and Modi, Kavan}, journal = {Phys. Rev. Lett.}, volume = {122}, pages = {140401}, year = {2019}, doi = {10.1103/PhysRevLett.122.140401}, archiveprefix = {arXiv}, eprint = {1805.11341}, }