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Unitary $t$-designs are the bread and butter of quantum information theory and beyond. An important issue in practice is that of efficiently constructing good approximations of such unitary $t$-designs. Building on results by Aubrun (Comm.…

Quantum Physics · Physics 2020-09-02 Cécilia Lancien , Christian Majenz

We develop the concept of a unitary t-design as a means of expressing operationally useful subsets of the stochastic properties of the uniform (Haar) measure on the unitary group U(2^n) on n qubits. In particular, sets of unitaries forming…

Quantum Physics · Physics 2015-06-26 Christoph Dankert , Richard Cleve , Joseph Emerson , Etera Livine

We propose the first continuous-variable (CV) unclonable encryption scheme, extending the paradigm of quantum encryption of classical messages (QECM) to CV systems. In our construction, a classical message is first encrypted classically and…

Quantum Physics · Physics 2025-12-19 Arpan Akash Ray , Boris Škorić

We introduce the notion of "non-malleability" of a quantum state encryption scheme (in dimension d): in addition to the requirement that an adversary cannot learn information about the state, here we demand that no controlled modification…

Quantum Physics · Physics 2017-08-01 Andris Ambainis , Jan Bouda , Andreas Winter

A unitary 2-design can be viewed as a quantum analogue of a 2-universal hash function: it is indistinguishable from a truly random unitary by any procedure that queries it twice. We show that exact unitary 2-designs on n qubits can be…

Quantum Physics · Physics 2017-01-03 Richard Cleve , Debbie Leung , Li Liu , Chunhao Wang

Epsilon-nets and approximate unitary $t$-designs are natural notions that capture properties of unitary operations relevant for numerous applications in quantum information and quantum computing. The former constitute subsets of unitary…

Quantum Physics · Physics 2021-11-02 Michał Oszmaniec , Adam Sawicki , Michał Horodecki

Unitary designs are unitary ensembles that emulate Haar-random unitary statistics. They provide a vital tool for studying quantum randomness and have found broad applications in quantum technologies. However, existing research has focused…

Quantum Physics · Physics 2026-01-06 Xiaodong Yang , Jiaqing Leng , Jun Li

We present an algorithm for efficiently approximating of qubit unitaries over gate sets derived from totally definite quaternion algebras. It achieves $\varepsilon$-approximations using circuits of length $O(\log(1/\varepsilon))$, which is…

Quantum Physics · Physics 2015-10-16 Vadym Kliuchnikov , Alex Bocharov , Martin Roetteler , Jon Yard

Unitary t-designs are some of the most versatile tools in quantum information theory. Their applications range from randomized benchmarking and shadow tomography, to more fundamental ones such as emulating quantum chaos and establishing…

Quantum Physics · Physics 2026-03-04 Namit Anand , Jeffrey Marshall , Jason Saied , Eleanor Rieffel , Andrea Morello

Random unitaries are useful in quantum information and related fields, but hard to generate with limited resources. An approximate unitary $k$-design is an ensemble of unitaries with an underlying measure over which the average is close to…

Quantum Physics · Physics 2026-02-09 Nicholas LaRacuente , Felix Leditzky

Continuous variable (CV) quantum computation offers an alternative to qubit-based computing by exploiting the infinite-dimensional Hilbert space of bosonic modes. Despite recent progress, superconducting platforms have yet to demonstrate a…

We generalize the notion of quantum state designs to infinite-dimensional spaces. We first prove that, under the definition of continuous-variable (CV) state $t$-designs from Comm. Math. Phys. 326, 755 (2014), no state designs exist for…

Quantum Physics · Physics 2024-06-18 Joseph T. Iosue , Kunal Sharma , Michael J. Gullans , Victor V. Albert

We construct $\varepsilon$-approximate unitary $k$-designs on $n$ qubits in circuit depth $O(\log k \log \log n k / \varepsilon)$. The depth is exponentially improved over all known results in all three parameters $n$, $k$, $\varepsilon$.…

Quantum Physics · Physics 2025-07-22 Laura Cui , Thomas Schuster , Fernando Brandao , Hsin-Yuan Huang

Unitary designs are essential tools in several quantum information protocols. Similarly to other design concepts, unitary designs are mainly used to facilitate averaging over a relevant space, in this case, the unitary group…

Quantum Physics · Physics 2026-02-25 Ágoston Kaposi , Zoltán Kolarovszki , Adrián Solymos , Zoltán Zimborás

Constrained devices, such as smart sensors, wearable devices, and Internet of Things nodes, are increasingly prevalent in society and rely on secure communications to function properly. These devices often operate autonomously, exchanging…

Continuous-Variable (CV) devices are a promising platform for demonstrating large-scale quantum information protocols. In this framework, we define a general quantum computational model based on a CV hardware. It consists of vacuum input…

Quantum Physics · Physics 2019-02-06 Tom Douce , Damian Markham , Elham Kashefi , Peter van Loock , Giulia Ferrini

We present the first device-independent quantum cryptography protocol for continuous variables. Our scheme is based on the Gottesman-Kitaev-Preskill encoding scheme whereby a qubit is embedded in the infinite-dimensional space of a quantum…

Quantum Physics · Physics 2014-10-24 Kevin Marshall , Christian Weedbrook

Many quantum information protocols require the implementation of random unitaries. Because it takes exponential resources to produce Haar-random unitaries drawn from the full $n$-qubit group, one often resorts to $t$-designs. Unitary…

Continuous-variable (CV) measurement-device-independent (MDI) quantum key distribution (QKD) is immune to imperfect detection devices, which can eliminate all kinds of attacks on practical detectors. Here we first propose a CV-MDI QKD…

Quantum Physics · Physics 2021-08-13 Dongyun Bai , Peng Huang , Yiqun Zhu , Hongxin Ma , Tailong Xiao , Tao Wang , Guihua Zeng

In recent years, continuous-variable quantum key distribution (CV-QKD) has become a promising paradigm for enabling secure communication among multiple end users sharing the same telecommunication backbone. CV-QKD with reverse…

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