



@article {2859,
	title = {Shadow process tomography of quantum channels},
	journal = {Phys. Rev. A},
	volume = {107},
	year = {2023},
	month = {4/4/2023},
	abstract = {<p>Quantum process tomography is a critical capability for building quantum computers, enabling quantum networks, and understanding quantum sensors. Like quantum state tomography, the process tomography of an arbitrary quantum channel requires a number of measurements that scale exponentially in the number of quantum bits affected. However, the recent field of shadow tomography, applied to quantum states, has demonstrated the ability to extract key information about a state with only polynomially many measurements. In this work, we apply the concepts of shadow state tomography to the challenge of characterizing quantum processes. We make use of the Choi isomorphism to directly apply rigorous bounds from shadow state tomography to shadow process tomography, and we find additional bounds on the number of measurements that are unique to process tomography. Our results, which include algorithms for implementing shadow process tomography enable new techniques including evaluation of channel concatenation and the application of channels to shadows of quantum states. This provides a dramatic improvement for understanding large-scale quantum systems.</p>},
	doi = {https://doi.org/10.1103/PhysRevA.107.042403},
	url = {https://arxiv.org/abs/2110.03629},
	author = {Jonathan Kunjummen and Minh C. Tran and Daniel Carney and Jacob M. Taylor}
}
@article {2403,
	title = {Signaling and Scrambling with Strongly Long-Range Interactions},
	journal = {Physical Review A},
	volume = {102},
	year = {2020},
	month = {7/8/2020},
	abstract = {<p>Strongly long-range interacting quantum systems---those with interactions decaying as a power-law 1/rα in the distance r on a D-dimensional lattice for α\&le;D---have received significant interest in recent years. They are present in leading experimental platforms for quantum computation and simulation, as well as in theoretical models of quantum information scrambling and fast entanglement creation. Since no notion of locality is expected in such systems, a general understanding of their dynamics is lacking. As a first step towards rectifying this problem, we prove two new Lieb-Robinson-type bounds that constrain the time for signaling and scrambling in strongly long-range interacting systems, for which no tight bounds were previously known. Our first bound applies to systems mappable to free-particle Hamiltonians with long-range hopping, and is saturable for α\&le;D/2. Our second bound pertains to generic long-range interacting spin Hamiltonians, and leads to a tight lower bound for the signaling time to extensive subsets of the system for all α\&lt;D. This result also lower-bounds the scrambling time, and suggests a path towards achieving a tight scrambling bound that can prove the long-standing fast scrambling conjecture.\&nbsp;</p>},
	doi = {https://journals.aps.org/pra/abstract/10.1103/PhysRevA.102.010401},
	url = {https://arxiv.org/abs/1906.02662},
	author = {Andrew Y. Guo and Minh C. Tran and Andrew M. Childs and Alexey V. Gorshkov and Zhe-Xuan Gong}
}
