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A collection of orthonormal bases for a complex dXd Hilbert space is called mutually unbiased (MUB) if for any two vectors v and w from different bases the square of the inner product equals 1/d: |<v,w>| ^{2}=1/d. The MUB problem is to…

Quantum Physics · Physics 2007-05-23 Arthur O. Pittenger , Morton H. Rubin

Quantum process tomography is a powerful tool for understanding quantum channels and characterizing properties of quantum devices. Inspired by recent advances using classical shadows in quantum state tomography [H.-Y. Huang, R. Kueng, and…

Quantum Physics · Physics 2024-02-12 Ryan Levy , Di Luo , Bryan K. Clark

Shadow tomography for quantum states provides a sample efficient approach for predicting the properties of quantum systems when the properties are restricted to expectation values of $2$-outcome POVMs. However, these shadow tomography…

Quantum Physics · Physics 2022-09-08 Weiyuan Gong , Scott Aaronson

We introduce Sketch Tomography, an efficient procedure for quantum state tomography based on the classical shadow protocol used for quantum observable estimations. The procedure applies to the case where the ground truth quantum state is a…

Quantum Physics · Physics 2026-05-27 Xun Tang , Haoxuan Chen , Yuehaw Khoo , Lexing Ying

We describe a particular class of pairs of quantum observables which are extremal in the convex set of all pairs of compatible quantum observables. The pairs in this class are constructed as uniformly noisy versions of two mutually unbiased…

Quantum Physics · Physics 2019-07-24 Claudio Carmeli , Gianni Cassinelli , Alessandro Toigo

We study sequential quantum changepoint detection in settings where the pre- and post-change regimes are specified through constraints on the expectation values of a finite set of observables. We consider an architecture with separate…

Quantum Physics · Physics 2026-02-13 Matteo Zecchin , Osvaldo Simeone , Aaditya Ramdas

We examine the problem of estimating the trace of a matrix $A$ when given access to an oracle which computes $x^\dagger A x$ for an input vector $x$. We make use of the basis vectors from a set of mutually unbiased bases, widely studied in…

Numerical Analysis · Computer Science 2016-08-02 J. K. Fitzsimons , M. A. Osborne , S. J. Roberts , J. F. Fitzsimons

Measurement based (MB) quantum computation allows for universal quantum computing by measuring individual qubits prepared in entangled multipartite states, known as graph states. Unless corrected for, the randomness of the measurements…

Quantum Physics · Physics 2018-02-28 Rawad Mezher , Joe Ghalbouni , Joseph Dgheim , Damian Markham

Quantum uncertainty relations impose fundamental limits on the joint knowledge that can be acquired from complementary observables: perfect knowledge of a quantum state in one basis implies maximal indetermination in all other mutually…

The notion of mutual unbiasedness for coarse-grained measurements of quantum continuous variable systems is considered. It is shown that while the procedure of "standard" coarse graining breaks the mutual unbiasedness between conjugate…

Quantum Physics · Physics 2018-01-25 Daniel S. Tasca , Piero Sánchez , Stephen P. Walborn , Łukasz Rudnicki

In this work quantum metrology techniques are applied to the imaging of objects with a non-uniform refractive spatial profile. A sensible improvement on the classical accuracy is shown to be found when the "Twin Beam State" (TWB) is used.…

Optics · Physics 2020-09-21 Giuseppe Ortolano , Ivano Ruo Berchera , Enrico Predazzi

In the framework of mutually unbiased bases (MUBs), a measurement in one basis gives \emph{no information} about the outcomes of measurements in another basis. Here, we relax the no-information condition by allowing the $d$ outcomes to be…

Quantum Physics · Physics 2025-12-18 Seyed Javad Akhtarshenas , Saman Karimi , Mahdi Salehi

In dimension $d$, Mutually Unbiased Bases (MUBs) are a collection of orthonormal bases over $\mathbb{C}^d$ such that for any two vectors $v_1, v_2$ belonging to different bases, the scalar product $|\braket{v_1|v_2}| = \frac{1}{\sqrt{d}}$.…

Discrete Mathematics · Computer Science 2024-03-15 Ajeet Kumar , Subhamoy Maitra , Somjit Roy

A pair of orthonormal bases is called mutually unbiased if all mutual overlaps between any element of one basis with an arbitrary element of the other basis coincide. In case the dimension, $d$, of the considered Hilbert space is a power of…

Quantum Physics · Physics 2013-11-27 Christoph Spengler , Barbara Kraus

Randomised measurements can efficiently characterise many-body quantum states by learning the expectation values of observables with low Pauli weights. In this paper, we generalise the theoretical tools of classical shadow tomography to the…

Quantum Physics · Physics 2026-02-05 Gregory A. L. White , Lloyd C. L. Hollenberg , Charles D. Hill , Kavan Modi

Quantum measurements play a fundamental role in quantum information. Therefore, increasing efforts are being made to construct symmetric measurement operators for qudit systems. A wide class of projective measurements corresponds to complex…

Quantum Physics · Physics 2026-01-06 Katarzyna Siudzińska

Quantum probes that enable enhanced exploration and characterization of complex systems are central to modern science, spanning applications from biology to astrophysics and chemical design. In large many-body quantum systems, interactions…

We consider the problem of mutually unbiased bases as a polynomial optimization problem over the reals. We heavily reduce it using known symmetries before exploring it using two methods, combining a number of optimization techniques. The…

Quantum Physics · Physics 2023-08-04 Luke Mortimer

Many hybrid quantum-classical algorithms for the application of ground state energy estimation in quantum chemistry involve estimating the expectation value of a molecular Hamiltonian with respect to a quantum state through measurements on…

We show that in a complex d-dimensional vector space, one can find O(d) bases whose elements form a 2-design. Such vector sets generalize the notion of a maximal collection of mutually unbiased bases (MUBs). MUBs have manifold applications…

Quantum Physics · Physics 2008-05-19 Gary McConnell , David Gross