All reports by Author Wei Zhan:

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TR23-196
| 7th December 2023
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Huacheng Yu, Wei Zhan#### Sampling, Flowers and Communication

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TR23-107
| 20th July 2023
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Uma Girish, Ran Raz, Wei Zhan#### Quantum Logspace Computations are Verifiable

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TR23-096
| 28th June 2023
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Huacheng Yu, Wei Zhan#### Randomized vs. Deterministic Separation in Time-Space Tradeoffs of Multi-Output Functions

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TR23-040
| 28th March 2023
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Edward Pyne, Ran Raz, Wei Zhan#### Certified Hardness vs. Randomness for Log-Space

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TR23-018
| 1st March 2023
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Qipeng Liu, Ran Raz, Wei Zhan#### Memory-Sample Lower Bounds for Learning with Classical-Quantum Hybrid Memory

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TR22-043
| 2nd April 2022
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Uma Girish, Kunal Mittal, Ran Raz, Wei Zhan#### Polynomial Bounds On Parallel Repetition For All 3-Player Games With Binary Inputs

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TR22-039
| 14th March 2022
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Uma Girish, Justin Holmgren, Kunal Mittal, Ran Raz, Wei Zhan#### Parallel Repetition For All 3-Player Games Over Binary Alphabet

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TR21-101
| 13th July 2021
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Uma Girish, Justin Holmgren, Kunal Mittal, Ran Raz, Wei Zhan#### A Parallel Repetition Theorem for the GHZ Game: A Simpler Proof

Revisions: 1

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TR20-101
| 7th July 2020
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Uma Girish, Ran Raz, Wei Zhan#### Lower Bounds for XOR of Forrelations

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TR20-087
| 8th June 2020
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Uma Girish, Ran Raz, Wei Zhan#### Quantum Logspace Algorithm for Powering Matrices with Bounded Norm

Revisions: 2

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TR19-162
| 15th November 2019
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Ran Raz, Wei Zhan#### The Random-Query Model and the Memory-Bounded Coupon Collector

Huacheng Yu, Wei Zhan

Given a distribution over $[n]^n$ such that any $k$ coordinates need $k/\log^{O(1)}n$ bits of communication to sample, we prove that any map that samples this distribution from uniform cells requires locality $\Omega(\log(n/k)/\log\log(n/k))$. In particular, we show that for any constant $\delta>0$, there exists $\varepsilon=2^{-\Omega(n^{1-\delta})}$ such that $\Omega(\log n/\log\log n)$ non-adaptive ... more >>>

Uma Girish, Ran Raz, Wei Zhan

In this note, we observe that quantum logspace computations are verifiable by classical logspace algorithms, with unconditional security. More precisely, every language in BQL has an information-theoretically secure) streaming proof with a quantum logspace prover and a classical logspace verifier. The prover provides a polynomial-length proof that is streamed to ... more >>>

Huacheng Yu, Wei Zhan

We prove the first polynomial separation between randomized and deterministic time-space tradeoffs of multi-output functions. In particular, we present a total function that on the input of $n$ elements in $[n]$, outputs $O(n)$ elements, such that:

- There exists a randomized oblivious algorithm with space $O(\log n)$, time $O(n\log n)$ ... more >>>

Edward Pyne, Ran Raz, Wei Zhan

Let $\mathcal{L}$ be a language that can be decided in linear space and let $\epsilon >0$ be any constant. Let $\mathcal{A}$ be the exponential hardness assumption that for every $n$, membership in $\mathcal{L}$ for inputs of length~$n$ cannot be decided by circuits of size smaller than $2^{\epsilon n}$.

We ...
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Qipeng Liu, Ran Raz, Wei Zhan

In a work by Raz (J. ACM and FOCS 16), it was proved that any algorithm for parity learning on $n$ bits requires either $\Omega(n^2)$ bits of classical memory or an exponential number (in~$n$) of random samples. A line of recent works continued that research direction and showed that for ... more >>>

Uma Girish, Kunal Mittal, Ran Raz, Wei Zhan

We prove that for every 3-player (3-prover) game $\mathcal G$ with value less than one, whose query distribution has the support $\mathcal S = \{(1,0,0), (0,1,0), (0,0,1)\}$ of hamming weight one vectors, the value of the $n$-fold parallel repetition $\mathcal G^{\otimes n}$ decays polynomially fast to zero; that is, there ... more >>>

Uma Girish, Justin Holmgren, Kunal Mittal, Ran Raz, Wei Zhan

We prove that for every 3-player (3-prover) game, with binary questions and answers and value less than $1$, the value of the $n$-fold parallel repetition of the game decays polynomially fast to $0$. That is, for every such game, there exists a constant $c>0$, such that the value of the ... more >>>

Uma Girish, Justin Holmgren, Kunal Mittal, Ran Raz, Wei Zhan

We give a new proof of the fact that the parallel repetition of the (3-player) GHZ game reduces the value of the game to zero polynomially quickly. That is, we show that the value of the $n$-fold GHZ game is at most $n^{-\Omega(1)}$. This was first established by Holmgren and ... more >>>

Uma Girish, Ran Raz, Wei Zhan

The Forrelation problem, first introduced by Aaronson [AA10] and Aaronson and Ambainis [AA15], is a well studied computational problem in the context of separating quantum and classical computational models. Variants of this problem were used to give tight separations between quantum and classical query complexity [AA15]; the first separation between ... more >>>

Uma Girish, Ran Raz, Wei Zhan

We give a quantum logspace algorithm for powering contraction matrices, that is, matrices with spectral norm at most 1. The algorithm gets as an input an arbitrary $n\times n$ contraction matrix $A$, and a parameter $T \leq poly(n)$ and outputs the entries of $A^T$, up to (arbitrary) polynomially small additive ... more >>>

Ran Raz, Wei Zhan

We study a new model of space-bounded computation, the {\it random-query} model. The model is based on a branching-program over input variables $x_1,\ldots,x_n$. In each time step, the branching program gets as an input a random index $i \in \{1,\ldots,n\}$, together with the input variable $x_i$ (rather than querying an ... more >>>