The past few years have witnessed the concrete and fast spreading of quantum technologies for practical computation and simulation. In particular, quantum computing platforms based on either trapped ...ions or superconducting qubits have become available for simulations and benchmarking, with up to few tens of qubits that can be reliably initialized, controlled, and measured. The present Review aims at giving a comprehensive outlook on the state‐of‐the‐art capabilities offered from these near‐term noisy devices as universal quantum simulators, that is, programmable quantum computers potentially able to calculate the time evolution of many physical models. First, a pedagogic overview on the basic theoretical background pertaining digital quantum simulations is given, with a focus on hardware‐dependent mapping of spin‐type Hamiltonians into the corresponding quantum circuit as a key initial step toward simulating more complex models. Then, the main experimental achievements obtained in the last decade are reviewed, focusing on the digital quantum simulation of such spin models by employing two leading quantum architectures. Their performances are compared, and future challenges are outlined, also in view of prospective hybrid technologies, towards the ultimate goal of reaching the long‐sought quantum advantage for the simulation of complex many‐body models in the physical sciences.
The theory and hardware implementations of universal quantum simulators are reviewed. Qubit‐based processors can be programmed to compute the dynamics of interesting many‐body systems, with a sequence of hardware‐compatible unitary operations and suitable measurements providing access to time‐evolved physical observables. Experimental results obtained on the currently leading technological platforms are summarized, with an outlook on future developments.
A switchable interaction between pairs of highly coherent qubits is a crucial ingredient for the physical realization of quantum information processing. One promising route to enable quantum logic ...operations involves the use of nuclear spins as protected elementary units of information, qubits. Here we propose a simple way to use fast electronic spin excitations to switch the effective interaction between nuclear spin qubits and the realization of a two-qubit molecular architecture based on highly coherent vanadyl moieties to implement quantum logic operations. Controlled generation of entanglement between qubits is possible here through chemically tuned magnetic coupling between electronic spins, which is clearly evidenced by the splitting of the vanadium(iv) hyperfine lines in the continuous-wave electron paramagnetic resonance spectrum. The system has been further characterized by pulsed electron paramagnetic resonance spectroscopy, evidencing remarkably long coherence times. The experimentally derived spin Hamiltonian parameters have been used to simulate the system dynamics under the sequence of pulses required to implement quantum gates in a realistic description that includes also the harmful effect of decoherence. This demonstrates the possibility of using this molecular complex to implement a control-Z (CZ) gate and simple quantum simulations. Indeed, we also propose a proof-of-principle experiment based on the simulation of the quantum tunneling of the magnetization in a
= 1 spin system.
The impact of intraoperative ventilation on postoperative pulmonary complications is not defined. The authors aimed at determining the effectiveness of protective mechanical ventilation during open ...abdominal surgery on a modified Clinical Pulmonary Infection Score as primary outcome and postoperative pulmonary function.
Prospective randomized, open-label, clinical trial performed in 56 patients scheduled to undergo elective open abdominal surgery lasting more than 2 h. Patients were assigned by envelopes to mechanical ventilation with tidal volume of 9 ml/kg ideal body weight and zero-positive end-expiratory pressure (standard ventilation strategy) or tidal volumes of 7 ml/kg ideal body weight, 10 cm H2O positive end-expiratory pressure, and recruitment maneuvers (protective ventilation strategy). Modified Clinical Pulmonary Infection Score, gas exchange, and pulmonary functional tests were measured preoperatively, as well as at days 1, 3, and 5 after surgery.
Patients ventilated protectively showed better pulmonary functional tests up to day 5, fewer alterations on chest x-ray up to day 3 and higher arterial oxygenation in air at days 1, 3, and 5 (mmHg; mean ± SD): 77.1 ± 13.0 versus 64.9 ± 11.3 (P = 0.0006), 80.5 ± 10.1 versus 69.7 ± 9.3 (P = 0.0002), and 82.1 ± 10.7 versus 78.5 ± 21.7 (P = 0.44) respectively. The modified Clinical Pulmonary Infection Score was lower in the protective ventilation strategy at days 1 and 3. The percentage of patients in hospital at day 28 after surgery was not different between groups (7 vs. 15% respectively, P = 0.42).
A protective ventilation strategy during abdominal surgery lasting more than 2 h improved respiratory function and reduced the modified Clinical Pulmonary Infection Score without affecting length of hospital stay.
Bit coin is the first digital currency to see widespread adoption. While payments are conducted between pseudonyms, Bit coin cannot offer strong privacy guarantees: payment transactions are recorded ...in a public decentralized ledger, from which much information can be deduced. Zero coin (Miers et al., IEEE S&P 2013) tackles some of these privacy issues by unlinking transactions from the payment's origin. Yet, it still reveals payments' destinations and amounts, and is limited in functionality. In this paper, we construct a full-fledged ledger-based digital currency with strong privacy guarantees. Our results leverage recent advances in zero-knowledge Succinct Non-interactive Arguments of Knowledge (zk-SNARKs). First, we formulate and construct decentralized anonymous payment schemes (DAP schemes). A DAP scheme enables users to directly pay each other privately: the corresponding transaction hides the payment's origin, destination, and transferred amount. We provide formal definitions and proofs of the construction's security. Second, we build Zero cash, a practical instantiation of our DAP scheme construction. In Zero cash, transactions are less than 1 kB and take under 6 ms to verify - orders of magnitude more efficient than the less-anonymous Zero coin and competitive with plain Bit coin.
The physical implementation of quantum information processing relies on individual modules-qubits-and operations that modify such modules either individually or in groups-quantum gates. Two examples ...of gates that entangle pairs of qubits are the controlled NOT-gate (CNOT) gate, which flips the state of one qubit depending on the state of another, and the gate that brings a two-qubit product state into a superposition involving partially swapping the qubit states. Here we show that through supramolecular chemistry a single simple module, molecular {Cr7Ni} rings, which act as the qubits, can be assembled into structures suitable for either the CNOT or gate by choice of linker, and we characterize these structures by electron spin resonance spectroscopy. We introduce two schemes for implementing such gates with these supramolecular assemblies and perform detailed simulations, based on the measured parameters including decoherence, to demonstrate how the gates would operate.
Periodontitis consists of a progressive destruction of tooth-supporting tissues. Considering that probiotics are being proposed as a support to the gold standard treatment Scaling-and-Root-Planing ...(SRP), this study aims to assess two new formulations (toothpaste and chewing-gum). 60 patients were randomly assigned to three domiciliary hygiene treatments: Group 1 (SRP + chlorhexidine-based toothpaste) (control), Group 2 (SRP + probiotics-based toothpaste) and Group 3 (SRP + probiotics-based toothpaste + probiotics-based chewing-gum). At baseline (T
) and after 3 and 6 months (T
-T
), periodontal clinical parameters were recorded, along with microbiological ones by means of a commercial kit. As to the former, no significant differences were shown at T
or T
, neither in controls for any index, nor in the experimental groups for adherent gingiva and gingival recession. Conversely, some significant differences were found in Group 2 and 3 for the other clinical indexes tested. Considering microbiological parameters, no significant differences were detected compared to baseline values for any group, except in Group 2 and 3 at T
only for the percentage of the orange complex pathogens and for the copies/microliter of
and
. Accordingly, although colonization of probiotic bacteria has not been assessed in this study, the probiotics tested represent a valid support to SRP with a benefit on several clinical indexes and on specific periodontopathogens. Despite this promising action, the relationship between the use of probiotics and improvement in clinical parameters is still unclear and deserves to be further explored.
Succinct non-interactive arguments
(SNARGs) enable verifying NP statements with lower complexity than required for classical NP verification. Traditionally, the focus has been on minimizing the ...length of such arguments; nowadays, researchers have focused also on minimizing verification time, by drawing motivation from the problem of delegating computation. A common relaxation is a
preprocessing
SNARG, which allows the verifier to conduct an expensive offline phase that is independent of the statement to be proven later. Recent constructions of preprocessing SNARGs have achieved attractive features: they are publicly-verifiable, proofs consist of only
O
(1) encrypted (or encoded) field elements, and verification is via arithmetic circuits of size linear in the NP statement. Additionally, these constructions seem to have “escaped the hegemony” of probabilistically-checkable proofs (PCPs) as a basic building block of succinct arguments. We present a general methodology for the construction of preprocessing
SNARG
s, as well as resulting new efficiency features. Our contribution is threefold:
(1)
We introduce and study a natural extension of the interactive proof model that considers
algebraically-bounded
provers; this new setting is analogous to the common study of algebraically-bounded “adversaries” in other fields, such as pseudorandomness and randomness extraction. More concretely, in this work we focus on linear (or affine) provers, and provide several constructions of (succinct two-message)
linear interactive proofs
(LIPs) for NP. Our constructions are based on general transformations applied to both
linear
PCPs (LPCPs) and traditional “unstructured” PCPs.
(2)
We give conceptually simple cryptographic transformations from LIPs to preprocessing SNARGs, whose security can be based on different forms of
linear targeted malleability
(implied by previous knowledge assumptions). Our transformations convert arbitrary (two-message) LIPs into designated-verifier SNARGs, and LIPs with degree-bounded verifiers into publicly-verifiable SNARGs. We also extend our methodology to obtain
zero-knowledge
LIPs and SNARGs. Our techniques yield SNARGs
of knowledge
and thus can benefit from known recursive composition and bootstrapping techniques.
(3)
Following this methodology, we exhibit several constructions achieving new efficiency features, such as “single-ciphertext preprocessing SNARGs.” We also offer a new perspective on existing constructions of preprocessing SNARGs, revealing a direct connection of these to LPCPs and LIPs.
Background
There is a paucity of data about the occurrence and risk factors of herpes simplex virus (HSV) reactivation among patients with severe COVID-19 presenting with acute respiratory distress ...syndrome (ARDS).
Methods
We performed a nested case-control study among a cohort of SARS-CoV-2 infected patients with ARDS. Between March and April 2020, all consecutive mechanically ventilated patients ≥18 years old with a positive PCR for SARS-CoV-2 on mucocutaneous samples were included in the study. We collected data on demographics, medical history, laboratory variables, administration of antivirals and other agents, respiratory and organ support procedures, microbiological results, and management of ARDS with prone positioning and the use of steroids. Univariate and multivariable Cox regression models were performed in order to identify predictors of HSV reactivation.
Results
Eighty-three patients with laboratory-confirmed SARS-CoV-2 infection were admitted to the ICU for mechanical ventilation. 18/83 (21.7%) patients developed mucocutaneous herpes simplex virus reactivation after a median of 17 days (IQR, 14–20). Prone positioning was the only independent risk factor for HSV reactivation (adj. hazard ratios, 1.60; 95% CI, 1.11–2.30; P = 0.009). All patients with mucocutaneous HSV reactivation were treated with antivirals. The outcome in terms of ventilator-associated pneumonia, catheter-related bloodstream infections, and in-hospital mortality was similar for patients with and without HSV reactivation.
Conclusions
HSV reactivation is frequent in COVID-19 patients with ARDS, especially if prolonged invasive mechanical ventilation with prone positioning is needed. Prompt testing for HSV and initiation of antiviral therapy should be performed in case of mucocutaneous lesions in this population.
The Hunting of the SNARK Bitansky, Nir; Canetti, Ran; Chiesa, Alessandro ...
Journal of cryptology,
10/2017, Volume:
30, Issue:
4
Journal Article
Peer reviewed
Open access
The existence of succinct non-interactive arguments for NP (i.e., non-interactive computationally sound proofs where the verifier’s work is essentially independent of the complexity of the NP ...non-deterministic verifier) has been an intriguing question for the past two decades. Other than CS proofs in the random oracle model (Micali in SIAM J Comput 30(4):1253–1298,
2000
), prior to our work the only existing candidate construction is based on an elaborate assumption that is tailored to a specific protocol (Di Crescenzo and Lipmaa in Proceedings of the 4th conference on computability in Europe,
2008
). We formulate a general and relatively natural notion of an
extractable collision-resistant hash function (ECRH)
and show that, if ECRHs exist, then a modified version of Di Crescenzo and Lipmaa’s protocol is a succinct non-interactive argument for NP. Furthermore, the modified protocol is actually a succinct non-interactive
adaptive argument of knowledge (SNARK)
. We then propose several candidate constructions for ECRHs and relaxations thereof. We demonstrate the applicability of SNARKs to various forms of delegation of computation, to succinct non-interactive zero-knowledge arguments, and to succinct two-party secure computation. Finally, we show that SNARKs essentially imply the existence of ECRHs, thus demonstrating the necessity of the assumption. Going beyond
ECRH
s, we formulate the notion of
extractable one-way functions
(
EOWF
s). Assuming the existence of a natural variant of
EOWF
s, we construct a two-message selective-opening-attack-secure commitment scheme and a three-round zero-knowledge argument of knowledge. Furthermore, if the
EOWF
s are concurrently extractable, the three-round zero-knowledge protocol is also concurrent zero knowledge. Our constructions circumvent previous black-box impossibility results regarding these protocols by relying on
EOWF
s as the non-black-box component in the security reductions.
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