Reqomp: Space-constrained Uncomputation for Quantum Circuits

Quantum circuits must run on quantum computers with tight limits on qubit and gate counts. To generate circuits respecting both limits, a promising opportunity is exploiting $uncomputation$ to trade qubits for gates. We present Reqomp, a method to automatically synthesize correct and efficient uncomputation of ancillae while respecting hardware constraints. For a given circuit, Reqomp can offer a wide range of trade-offs between tightly constraining qubit count or gate count. Our evaluation demonstrates that Reqomp can significantly reduce the number of required ancilla qubits by up to 96%. On 80% of our benchmarks, the ancilla qubits required can be reduced by at least 25% while never incurring a gate count increase beyond 28%

Universal equivalence and majority of probabilistic programs over finite fields

We study decidability problems for equivalence of probabilistic programs, for a core probabilistic programming language over finite fields of fixed characteristic. The programming language supports uniform sampling, addition, multiplication and conditionals and thus is sufficiently expressive to encode boolean and arithmetic circuits. We consider two variants of equivalence: the first one considers an interpretation over a fixed finite field, while the second one, which we call universal equivalence, verifies equivalence over all extensions of a finite field. The universal variant typically arises in provable cryptography when one wishes to prove equivalence for any length of bitstrings, i.e., elements of extensions of the boolean field. While the first problem is obviously decidable, we establish its exact complexity which lies in the counting hierarchy. To show decidability, and a doubly exponential upper bound, of the universal variant we rely on results from algorithmic number theory and the possibility to compare local zeta functions associated to given polynomials. Finally we study several variants of the equivalence problem, including a problem we call majority, motivated by differential privacy

High-Level Quantum Programming

Quantum computation has made remarkable progress in recent years, not only by constructing quantum computers that surpass classical counterparts in specific tasks, but also by developing increasingly complex quantum algorithms. Unfortunately, the development of essential tools for quantum programming, such as high-level programming languages and debugging tools, has not kept pace with these advancements. Therefore, the goal of this thesis is to advance quantum computation by introducing novel tools that both enable experts to fully leverage the potential of quantum computing and lower the entrance barrier for non-expert quantum programmers. To this end, the thesis presents three innovative tools: Silq, Unqomp, and Abstraqt. Silq is a high-level quantum programming language whose most significant contribution is its ability to ensure all temporary quantum values can be automatically uncomputed, simplifying the programming process. Unqomp is the first procedure to automatically synthesize uncomputation within quantum circuits containing non-classical gates, such as the Hadamard gate. Abstraqt is a novel approach to efficiently simulate arbitrary quantum circuits at the cost of lost precision, enabling the study of circuit properties that were previously intractable. These tools were inspired by established techniques from the programming languages community, which can serve as a rich reservoir of concepts and approaches beneficial for quantum computing. Silq utilizes a novel type system to enable uncomputation, Unqomp synthesizes uncomputation through a graph representation of quantum circuits, and Abstraqt leverages abstract interpretation to abstract the imprecision it introduces. Overall, these tools improve the productivity of quantum programmers and reduce the likelihood of errors in quantum algorithm implementations

ATMOSPHERE CREATING LIGHT IN MUSEUM AND ART GALLERY SPACES : A study about the interplay between light and spatiality

A lot of research on the experience of atmosphere uses physical measurements. However, a recognised idea among lighting designers is that these physical values and the experience of light is not always the same, which makes it relevant to work more with visual observations to understand and analyse spatiality and the effects of light. The purpose of the study was to investigate how spaciousness and atmosphere in museum and art gallery environments can be linked to their lighting and art. This is to provide an increased understanding of how light affects spatiality and how it relates to the room’s atmosphere, and to be able to see how the atmosphere is experienced in connection with the exhibits. The study was conducted through visual observations during site visits, for each evaluated room at each museum and art gallery. The rooms were analyzed using the PERCIFAL and Branzell methods, but the values of illuminance, color temperature, color rendering index, and spectral power distribution were also documented. Additionally, an online survey was sent out to collect further data concerning the experience of atmosphere. Part 1 was quantitative and focused on atmosphere words and was judged on a 7-point scale, while Part 2 was qualitative and focused on the connection between the exhibited object and the room. Here, the respondents responded in text form. The result of the study shows that the experience of atmosphere is affected by the interplay between light and spatiality, and that it is not one lone parameter that is decisive. The respondents thought that an interplay between atmosphere and the exhibited object could elevate the experience of art, and that light was a big part of how the room and its atmosphere was experienced. This shows that there are opportunities to work more with lighting in gallery spaces to create an atmosphere that connect more with exhibitions and objects. The study was limited to art-related exhibitions in Sweden. Due to the study was conducted in a very specific context it can not be said with certainty to be generally valid, though parts of the result pertaining to the atmosphere affecting parameters are likely able to use in other situations.Mycket forskning om atmosfärsupplevelse använder sig av fysikaliska mätningar. En vedertagen idé bland ljusdesigners är dock att fysikaliska värden och det upplevda ljuset inte alltid är detsamma, vilket gör att det blir relevant att arbeta mer med visuella observationer för att förstå och analysera rumslighet och ljusets påverkan. Syftet med studien var att undersöka hur rumslighet och atmosfär i musei- och konsthallsmiljöer kan kopplas till deras belysning och konst. Detta för att ge en ökad förståelse kring hur ljuset påverkar rumsligheten och hur det anknyter till rumsatmosfären, samt att kunna se hur atmosfären upplevs i anknytning till utställningsföremålen. Studien utfördes genom visuella observationer under platsbesök i respektive rum för varje museum och konsthall. Rummen analyserades genom metoderna PERCIFAL och Branzellmetoden, men även fysikaliska värden som belysningsstyrka, färgtemperatur, färgåtergivning och spektralfördelning dokumenterades. Slutligen skickades en digital enkät i två delar ut. Del 1 var kvantitativ och fokuserade på atmosfärsord och bedömdes på en 7-gradig skala, medan Del 2 var kvalitativ och fokuserade på kopplingen mellan utställningsföremålet och rummet. Här hade respondenterna möjligheten att svara i textform. Resultatet i studien visar att atmosfärsupplevelsen påverkas av samspelet mellan ljus och rum, och att det inte är en enskild parameter som avgör. Respondenterna ansåg att ett samspel mellan atmosfär och utställningsföremål kunde förhöja upplevelsen av konst och att ljus hade en tydlig påverkan för hur rummet och dess atmosfär uppfattades. Detta visar på att det finns möjligheter att arbeta mer med ljus i utställningslokaler för att skapa en atmosfär som samspelar mer med utställningar och utställningsföremål. Studien har begränsats till enbart konstutställningar på museer och konsthallar i Sverige. Utifrån att detta arbete genomfördes i denna specifika kontext kan det inte med säkerhet sägas vara generellt giltigt, men vissa delar av resultatet kring de atmosfärspåverkande parametrarna är sannolikt möjliga att överföra i andra situationer

Abstraqt: Analysis of Quantum Circuits via Abstract Stabilizer Simulation

Stabilizer simulation can efficiently simulate an important class of quantum circuits consisting exclusively of Clifford gates. However, all existing extensions of this simulation to arbitrary quantum circuits including non-Clifford gates suffer from an exponential runtime. To address this challenge, we present a novel approach for efficient stabilizer simulation on arbitrary quantum circuits, at the cost of lost precision. Our key idea is to compress an exponential sum representation of the quantum state into a single abstract summand covering (at least) all occurring summands. This allows us to introduce an abstract stabilizer simulator that efficiently manipulates abstract summands by over−approximating the effect of circuit operations including Clifford gates, non-Clifford gates, and (internal) measurements. We implemented our abstract simulator in a tool called Abstraqt and experimentally demonstrate that Abstraqt can establish circuit properties intractable for existing techniques.ISSN:2521-327

Unqomp: Synthesizing uncomputation in Quantum circuits

A key challenge when writing quantum programs is the need for uncomputation: temporary values produced during the computation must be reset to zero before they can be safely discarded. Unfortunately, most existing quantum languages require tedious manual uncomputation, often leading to inefficient and error-prone programs. We present Unqomp, the first procedure to automatically synthesize uncomputation in a given quantum circuit. Unqomp can be readily integrated into popular quantum languages, allowing the programmer to allocate and use temporary values analogously to classical computation, knowing they will be uncomputed by Unqomp. Our evaluation shows that programs leveraging Unqomp are not only shorter (-19% on average), but also generate more efficient circuits (-71% gates and-19% qubits on average)

DP-Sniper: Black-box discovery of differential privacy violations using classifiers

We present DP-Sniper, a practical black-box method that automatically finds violations of differential privacy.DP-Sniper is based on two key ideas: (i) training a classifier to predict if an observed output was likely generated from one of two possible inputs, and (ii) transforming this classifier into an approximately optimal attack on differential privacy.Our experimental evaluation demonstrates that DP-Sniper obtains up to 12.4 times stronger guarantees than state-of-the-art, while being 15.5 times faster. Further, we show that DP-Sniper is effective in exploiting floating-point vulnerabilities of naively implemented algorithms: it detects that a supposedly 0.1-differentially private implementation of the Laplace mechanism actually does not satisfy even 0.25-differential privacy