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In this paper, I take a step toward answering the following question: for m different small circuits that compute m orthogonal n qubit states, is there a small circuit that will map m computational basis states to these m states without any…

Computational Complexity · Computer Science 2019-06-26 Joshua Alan Cook

Reducing circuit depth and identifying an optimal trade-off between circuit depth and width is crucial for successful quantum computation. In this context, midcircuit measurement and feedforward have been shown to significantly reduce the…

Quantum Physics · Physics 2025-06-03 Hyeonjun Yeo , Ha Eum Kim , IlKwon Sohn , Kabgyun Jeong

Dynamic quantum circuits incorporate mid-circuit measurements and feed-forward operations originally intended to realize Quantum Error Correction. This paradigm has recently been utilized to prepare certain states and long-range entangling…

We present a deterministic framework for preparing an arbitrary three-qubit pure state. To leverage entanglement structure in the state-preparation task, we classify three-qubit pure states into five types with respect to a $1|2$…

Quantum Physics · Physics 2026-03-03 Yonghae Lee , Taewan Kim

Preparing quantum states is a fundamental task in various quantum algorithms. In particular, state preparation in quantum harmonic oscillators (HOs) is crucial for the creation of qudits and the implementation of high-dimensional…

Quantum Physics · Physics 2026-02-24 Nicolas Parra-A , Vladimir Vargas-Calderón , Herbert Vinck-Posada

Quantum state tomography (QST) is one of the fundamental problems in quantum information. Among various metrics, sample complexity is widely used to evaluate QST algorithms. While multi-copy measurements are known to achieve optimal sample…

Quantum Physics · Physics 2025-09-17 Gyungmin Cho , Dohun Kim

Quantum error correction and fault-tolerant quantum computation are two fundamental concepts which make quantum computing feasible. While providing a theoretical means with which to ensure the arbitrary accuracy of any quantum circuit,…

Quantum Physics · Physics 2007-05-23 A. M. Stephens , S. J. Devitt , A. G. Fowler , J. C. Ang , L. C. L. Hollenberg

We study the problem of state synthesis in the DQC1 (One Clean Qubit) model of quantum computation, which provides a single pure qubit and $n$ maximally mixed qubits, and after applying any quantum circuit some subset of the qubits are…

Quantum Physics · Physics 2024-04-08 Zachary Stier

Loading classical data into quantum registers is one of the most important primitives of quantum computing. While the complexity of preparing a generic quantum state is exponential in the number of qubits, in many practical tasks the state…

Quantum Physics · Physics 2022-09-02 Fereshte Mozafari , Giovanni De Micheli , Yuxiang Yang

Adaptive quantum circuits, leveraging measurements and classical feedback, significantly expand the landscape of realizable quantum states compared to their non-adaptive counterparts, enabling the preparation of long-range entangled states…

Quantum Physics · Physics 2025-09-23 Guoding Liu , Junjie Chen , Xiongfeng Ma

Quantum key distribution (QKD) could be the most significant application of quantum information theory. In nearly four decades, although substantial QKD protocols are developed, the BB84 protocol and its variants are still the most…

Quantum Physics · Physics 2023-08-22 Hao Shu

We propose a co-designed variant of ADAPT-VQE (Co-ADAPT-VQE) where the quantum hardware is taken into account in the construction of the ansatz. This framework can be readily used to optimize state preparation circuits for any device,…

We present two scalable and entanglement-free methods for estimating the collective state of an n-qubit quantum computer. The first method consists of a fixed set of five quantum circuits-regardless of the number of qubits-that avoid the…

In this thesis we examine a variety of techniques for reducing the resources required for fault-tolerant quantum computation. First, we show how to simplify universal encoded computation by using only transversal gates and standard error…

Quantum Physics · Physics 2014-10-21 Adam Paetznick

Fault-tolerant quantum computing typically requires the transpilation of arbitrary quantum circuits into a finite, universal gate set, such as Clifford+T. As a baseline, Diagonal approximation can be used for synthesizing single-qubit Pauli…

Quantum Physics · Physics 2026-05-12 Gilad Kishony , Avi Elazari , Ron Cohen , Lior Gazit

For parameter estimation from an $N$-component composite quantum system, it is known that a separable preparation leads to a mean-squared estimation error scaling as $1/N$ while an entangled preparation can in some conditions afford a…

Quantum Physics · Physics 2019-04-04 Francois Chapeau-Blondeau

The optimization of quantum circuit depth is crucial for practical quantum computing, as limited coherence times and error-prone operations constrain executable algorithms. Measurement and feedback operations are fundamental in quantum…

Quantum Physics · Physics 2025-03-21 Wei Zi , Junhong Nie , Xiaoming Sun

Quantum error correction is vital for implementing universal quantum computing. A key component is the encoding circuit that maps a product state of physical qubits into the encoded multipartite entangled logical state. Known methods are…

Quantum Physics · Physics 2021-04-07 Xiaosi Xu , Simon C. Benjamin , Xiao Yuan

Quantum state tomography (QST) for reconstructing pure states requires exponentially increasing resources and measurements with the number of qubits by using state-of-the-art quantum compressive sensing (CS) methods. In this article, QST…

Quantum Physics · Physics 2021-11-16 Burhan Gulbahar

Efficient preparation of arbitrary entangled quantum states is crucial for quantum computation. This is particularly important for noisy intermediate scale quantum simulators relying on variational hybrid quantum-classical algorithms. To…

Quantum Physics · Physics 2024-11-18 Ananda Roy , Sameer Erramilli , Robert M. Konik