arXiv subjects

Piyush P Kurur

Publications and source records attributed to Piyush P Kurur.

7 recordsLinked to original sources

arXiv2026

Improved Tristate Multiplication With Formalization in Rocq

We give a new multiplication algorithm for tristate numbers improving upon the state-of-the-art implementation from the Linux kernel in terms of precision and formal proofs. Our algorithm is significantly more precise as shown by experimental evaluation (at the peak, giving better results in 95.59% cases compared to the previous work for 31-bit samples). Importantly, we achieve this additional precision with performance comparable to the previous algorithm, as demonstrated by benchmarks. Finally, we formalize and prove the soundness of the algorithm in the Rocq proof assistant, adding to the trust in the resulting implementation. Our algorithm is now part of the upstream Linux kernel. Our soundness proof in Rocq for the new multiplication algorithm works for all bit widths, while the SAT/SMT-based machine-checked proof accompanying the previous algorithm was restricted to 8 bits. We also provide Rocq proofs for the soundness and optimality of the newly added tnum union operation and the existing tnum addition algorithm from the Linux kernel. Our optimality proof for tnum addition presents a simpler and straightforward lemma compared to prior work.

cs.LO↗

arXiv2011

Quantum Cyclic Code of length dividing $p^{t}+1$

In this paper, we study cyclic stabiliser codes over $\mathbb{F}_p$ of length dividing $p^t+1$ for some positive integer $t$. We call these $t$-Frobenius codes or just Frobenius codes for short. We give methods to construct them and show that they have efficient decoding algorithms. An important subclass of stabiliser codes are the linear stabiliser codes. For linear Frobenius codes we have stronger results: We completely characterise all linear Frobenius codes. As a consequence, we show that for every integer $n$ that divides $p^t+1$ for an odd $t$, there are no linear cyclic codes of length $n$. On the other hand for even $t$, we give an explicit method to construct all of them. This gives us a many explicit example of Frobenius codes which include the well studied Laflamme code. We show that the classical notion of BCH distance can be generalised to all the Frobenius codes that we construct, including the non-linear ones, and show that the algorithm of Berlekamp can be generalised to correct quantum errors within the BCH limit. This gives, for the first time, a family of codes that are neither CSS nor linear for which efficient decoding algorithm exits. The explicit examples that we construct are summarised in Table \ref{tab:explicit-examples-short} and explained in detail in Tables \ref{tab:explicit-examples-2} (linear case) and \ref{tab:explicit-examples-3} (non-linear case).

cs.IT↗

arXiv2010

Quantum Cyclic Code

In this paper, we define and study \emph{quantum cyclic codes}, a generalisation of cyclic codes to the quantum setting. Previously studied examples of quantum cyclic codes were all quantum codes obtained from classical cyclic codes via the CSS construction. However, the codes that we study are much more general. In particular, we construct cyclic stabiliser codes with parameters $[[5,1,3]]$, $[[17,1,7]]$ and $[[17,9,3]]$, all of which are \emph{not} CSS. The $[[5,1,3]]$ code is the well known Laflamme code and to the best of our knowledge the other two are new examples. Our definition of cyclicity applies to non-stabiliser codes as well; in fact we show that the $((5,6,2))$ nonstabiliser first constructed by Rains\etal~ cite{rains97nonadditive} and latter by Arvind \etal~\cite{arvind:2004:nonstabilizer} is cyclic. We also study stabiliser codes of length $4^m +1$ over $\mathbb{F}_2$ for which we define a notation of BCH distance. Much like the Berlekamp decoding algorithm for classical BCH codes, we give efficient quantum algorithms to correct up to $\floor{\frac{d-1}{2}}$ errors when the BCH distance is $d$.

cs.IT↗

arXiv2009

Representating groups on graphs

In this paper we formulate and study the problem of representing groups on graphs. We show that with respect to polynomial time turing reducibility, both abelian and solvable group representability are all equivalent to graph isomorphism, even when the group is presented as a permutation group via generators. On the other hand, the representability problem for general groups on trees is equivalent to checking, given a group $G$ and $n$, whether a nontrivial homomorphism from $G$ to $S_n$ exists. There does not seem to be a polynomial time algorithm for this problem, in spite of the fact that tree isomorphism has polynomial time algorithm.

cs.CC↗

arXiv2008

Fast Integer Multiplication using Modular Arithmetic

We give an $O(N\cdot \log N\cdot 2^{O(\log^*N)})$ algorithm for multiplying two $N$-bit integers that improves the $O(N\cdot \log N\cdot \log\log N)$ algorithm by Schönhage-Strassen. Both these algorithms use modular arithmetic. Recently, Fürer gave an $O(N\cdot \log N\cdot 2^{O(\log^*N)})$ algorithm which however uses arithmetic over complex numbers as opposed to modular arithmetic. In this paper, we use multivariate polynomial multiplication along with ideas from Fürer's algorithm to achieve this improvement in the modular setting. Our algorithm can also be viewed as a $p$-adic version of Fürer's algorithm. Thus, we show that the two seemingly different approaches to integer multiplication, modular and complex arithmetic, are similar.

cs.SC↗

arXiv2006

A Polynomial Time Nilpotence Test for Galois Groups and Related Results

We give a deterministic polynomial-time algorithm to check whether the Galois group $\Gal{f}$ of an input polynomial $f(X) \in \Q[X]$ is nilpotent: the running time is polynomial in $\size{f}$. Also, we generalize the Landau-Miller solvability test to an algorithm that tests if $\Gal{f}$ is in $Γ_d$: this algorithm runs in time polynomial in $\size{f}$ and $n^d$ and, moreover, if $\Gal{f}\inΓ_d$ it computes all the prime factors of $# \Gal{f}$.

cs.CC↗

arXiv2002

Nonstabilizer Quantum Codes from Abelian Subgroups of the Error Group

This paper is motivated by the computer-generated nonadditive ((5,6,2)) code described in an article by Rains, Hardin, Shor and Sloane. We describe a theory of non-stabilizer codes of which the nonadditive code of Rains et al is an example. Furthermore, we give a general strategy of constructing good nonstabilizer codes from good stabilizer codes and give some explicit constructions and asymptotically good nonstabilizer codes. In fact, we explicitly construct a family of distance 2 non-stabilizer codes over all finite fields of which the ((5,6,2)) is an special example. More interestingly, using our theory, we are also able to explicitly construct examples of non-stablizer quantum codes of distance 3. Like in the case of stabilizer codes, we can design fairly efficient encoding and decoding procedures.

quant-ph↗