Single-qubit gate teleportation provides a quantum advantage

Gate-teleportation circuits are arguably among the most basic examples of computations believed to provide a quantum computational advantage: In seminal work [Quantum Inf. Comput., 4(2):134--145], Terhal and DiVincenzo have shown that these circuits elude simulation by efficient classical algorithms under plausible complexity-theoretic assumptions. Here we consider possibilistic simulation [Phys. Rev. A 106, 062430 (2022)], a particularly weak form of this task where the goal is to output any string appearing with non-zero probability in the output distribution of the circuit. We show that even for single-qubit Clifford-gate-teleportation circuits this simulation problem cannot be solved by constant-depth classical circuits with bounded fan-in gates. Our results are unconditional and are obtained by a reduction to the problem of computing the parity, a well-studied problem in classical circuit complexity.Comment: 31 pages 10 figures. Typos fixed. New Section 3.3.3 Other word problems for Clifford modulo Pauli group

Single-shot decoding of good quantum LDPC codes

Quantum Tanner codes constitute a family of quantum low-density parity-check (LDPC) codes with good parameters, i.e., constant encoding rate and relative distance. In this article, we prove that quantum Tanner codes also facilitate single-shot quantum error correction (QEC) of adversarial noise, where one measurement round (consisting of constant-weight parity checks) suffices to perform reliable QEC even in the presence of measurement errors. We establish this result for both the sequential and parallel decoding algorithms introduced by Leverrier and Z\'emor. Furthermore, we show that in order to suppress errors over multiple repeated rounds of QEC, it suffices to run the parallel decoding algorithm for constant time in each round. Combined with good code parameters, the resulting constant-time overhead of QEC and robustness to (possibly time-correlated) adversarial noise make quantum Tanner codes alluring from the perspective of quantum fault-tolerant protocols.Comment: 35 pages, 3 figure

Criticality without frustration for quantum spin-1 chains

Frustration-free (FF) spin chains have a property that their ground state minimizes all individual terms in the chain Hamiltonian. We ask how entangled the ground state of a FF quantum spin-s chain with nearest-neighbor interactions can be for small values of s. While FF spin-1/2 chains are known to have unentangled ground states, the case s=1 remains less explored. We propose the first example of a FF translation-invariant spin-1 chain that has a unique highly entangled ground state and exhibits some signatures of a critical behavior. The ground state can be viewed as the uniform superposition of balanced strings of left and right parentheses separated by empty spaces. Entanglement entropy of one half of the chain scales as log(n)/2 + O(1), where n is the number of spins. We prove that the energy gap above the ground state is polynomial in 1/n. The proof relies on a new result concerning statistics of Dyck paths which might be of independent interest.Comment: 11 pages, 2 figures. Version 2: minor changes in the proof of Lemma

Early hand and mechanical leaf removal on yeld and some uvological charachteristic of cv. Cabernet Sauvignon (Vitis vinifera L.)

Defolijacija je bitan ampelotehnički zahvat u vinogradarskoj proizvodnji. Predmet ovoga istraživanja bio je utjecaj rane ručne i strojne defolijacije na prinos i neke uvološke karakteristike kultivara Cabernet sauvignon (Vitis vinifera L.) u odnosu na kotrolni tretman (bez defolijacije). Istraživanje je provedeno tijekom 2012. godine, a defolijacija obavljena neposredno prije cvatnje. Strojna defolijacija obavljena je bočnim traktorskim priključkom, dok je ručnom defolijacijom na svakoj mladici uklonjeno šest listova kako bi se postigla dobra izloženost grozdova svjetlosti. Iako su uočene relativne razlike između pojedinih tretmana za određena ispitivana svojstva samo je ručna defolijacija statistički značajno smanjila prinos u odnosu na kontrolni tretman.Defoliation is important viticultural practices in grape production. The subject of the study was the impact of early defoliation hand and machine on the yield and some uvological characteristics of cv. Cabernet Sauvignon ( Vitis vinifera L.) in regards to control treatment (without defoliation). The study was conducted during 2012th year and defoliation performed just before flowering. Machining defoliation was carried out side the tractor connection, while the manual defoliation on each shoot was removed six sheets to achieve a good exposure clusters. Despite the fact that there are some relative differences between treatments only hand defoliation statistical significantly affected one yield comapred to control treatment

SVJETSKA PROIZVODNJA PLODOVA VOĆA I GROŽĐA U SVIJETU KROZ 10 GODINA

Rad ne sadrži sažetak

Early hand and mechanical leaf removal on yeld and some uvological charachteristic of cv. Cabernet Sauvignon (Vitis vinifera L.)

Defolijacija je bitan ampelotehnički zahvat u vinogradarskoj proizvodnji. Predmet ovoga istraživanja bio je utjecaj rane ručne i strojne defolijacije na prinos i neke uvološke karakteristike kultivara Cabernet sauvignon (Vitis vinifera L.) u odnosu na kotrolni tretman (bez defolijacije). Istraživanje je provedeno tijekom 2012. godine, a defolijacija obavljena neposredno prije cvatnje. Strojna defolijacija obavljena je bočnim traktorskim priključkom, dok je ručnom defolijacijom na svakoj mladici uklonjeno šest listova kako bi se postigla dobra izloženost grozdova svjetlosti. Iako su uočene relativne razlike između pojedinih tretmana za određena ispitivana svojstva samo je ručna defolijacija statistički značajno smanjila prinos u odnosu na kontrolni tretman.Defoliation is important viticultural practices in grape production. The subject of the study was the impact of early defoliation hand and machine on the yield and some uvological characteristics of cv. Cabernet Sauvignon ( Vitis vinifera L.) in regards to control treatment (without defoliation). The study was conducted during 2012th year and defoliation performed just before flowering. Machining defoliation was carried out side the tractor connection, while the manual defoliation on each shoot was removed six sheets to achieve a good exposure clusters. Despite the fact that there are some relative differences between treatments only hand defoliation statistical significantly affected one yield comapred to control treatment