Which term refers to the strong information correlation between qubits

In this article Just as bits are the fundamental object of information in classical computing, qubits (quantum bits) are the fundamental object of information in quantum computing. To understand this correspondence, this article looks at the simplest example: a single qubit. Representing a qubit While a bit, or binary digit, can have a value either $0$ or $1$, a qubit can have a value that is either $0$, $1$ or a quantum superposition of $0$ and $1$. The state of a single qubit can be described by a two-dimensional column vector of unit norm, that is, the magnitude squared of its entries must sum to $1$. This vector, called the quantum state vector, holds all the information needed to describe the one-qubit quantum system just as a single bit holds all of the information needed to describe the state of a binary variable. Any two-dimensional column vector of real or complex numbers with norm $1$ represents a possible quantum state held by a qubit. Thus $\begin R_x(\beta)R_z(\gamma)R_x(\delta)$. Thus $R_z(\theta)$ and $H$ also form a universal gate set although it is not a discrete set because $\theta$ can take any value. For this reason, and due to applications in quantum simulation, such continuous gates are crucial for quantum computation, especially at the quantum algorithm design level. To achieve fault-tolerant hardware implementation, they will ultimately be compiled into discrete gate sequences that closely approximate these rotations.

Superconducting qubits are a leading candidate for quantum computing but display temporal fluctuations in their energy relaxation times T 1. This introduces instabilities in multi-qubit device performance. Furthermore, autocorrelation in these time fluctuations introduces challenges for obtaining representative measures of T 1 for process optimization and device screening. These T 1 fluctuations are often attributed to time varying coupling of the qubit to defects, putative two level systems (TLSs). In this work, we develop a technique to probe the spectral and temporal dynamics of T 1 in single junction transmons by repeated T 1 measurements in the frequency vicinity of the bare qubit transition, via the AC-Stark effect. Across 10 qubits, we observe strong correlations between the mean T 1 averaged over approximately nine months and a snapshot of an equally weighted T 1 average over the Stark shifted frequency range. These observations are suggestive of an ergodic-like spectral diffusion of TLSs dominating T 1, and offer a promising path to more rapid T 1 characterization for device screening and process optimization. Superconducting qubits are a leading platform for quantum computing f α) in their energy relaxation times T 1 The fluctuations of qubit T 1 are often attributed to resonant couplings with two-level systems (TLSs) that have been historically studied in the context of amorphous solids T 1 in flux and stress tunable devices T 1 over time is explained Furthermor...

Quantum computing is computer architecture that is based upon quantum theory principles; these computers are much faster and much more expensive, but they promise a future of ridiculous speeds and processing power. A quantum computer does not use traditional bits and bytes but rather qubits. A qubit is like a bit, in that it is 1 or 0. In quantum computing, a qubit is the elementary unit (vs. a bit in the device you are using). However, since quantum computing is built upon quantum physics, a qubit can be BOTH a 1 or 0. This is called superposition; a particle can be in simultaneous states. Superposition Let's look at an example of a 2-qubit system/input to showcase entanglement. Entanglement means that quantum components (qubits, photons) are connected, or entangled, even if they are light-years away from each other! We don't yet know how this happens, only that it does. For example, if you measure an entangled qubit, the measurement will always correlate to the measure of the other entangled qubit. OK, so let's look at the two-qubit system with four initial states. We've talked about 2-qubit systems, but a quantum register is a system of any given number of qubits ( n-qubits). In such a register, there is any number of 2 n states. Because of quantum mechanics, superposition is at play; the state of the quantum computer can be in a superposition of any of these states. In a quantum computer, qubits are identified with an index in the register (starting at 0). A 3-qubit sy...

Most works on open quantum systems generally focus on the reduced physical system by tracing out the environment degrees of freedom. Here we show that the qubit distributions with the environment are essential for a thorough analysis and demonstrate that the way that quantum correlations are distributed in a quantum register is constrained by the way in which each subsystem gets correlated with the environment. For a two-qubit system coupled to a common dissipative environment , we show how to optimise interqubit correlations and entanglement via a quantification of the qubit-environment information flow, in a process that, perhaps surprisingly, does not rely on the knowledge of the state of the environment. To illustrate our findings, we consider an optically-driven bipartite interacting qubit AB system under the action of . By tailoring the light-matter interaction, a relationship between the qubits early stage disentanglement and the qubit-environment entanglement distribution is found. We also show that, under suitable initial conditions, the qubits energy asymmetry allows the identification of physical scenarios whereby qubit-qubit entanglement minima coincide with the extrema of the and entanglement oscillations. The quantum properties of physical systems have been studied for many years as crucial resources for quantum processing tasks and quantum information protocols Many works devoted to the study of entanglement and correlations dynamics in open quantum systems ...

• Perspective • 07 July 2020 Exploiting chemistry and molecular systems for quantum information science • ORCID: orcid.org/0000-0003-2920-5440 • • ORCID: orcid.org/0000-0003-0945-1492 • • • • • ORCID: orcid.org/0000-0002-2579-8835 • • • ORCID: orcid.org/0000-0002-1479-3318 • • • • ORCID: orcid.org/0000-0003-4255-9550 • … • Show authors Nature Reviews Chemistry volume 4, pages 490–504 ( 2020) The power of chemistry to prepare new molecules and materials has driven the quest for new approaches to solve problems having global societal impact, such as in renewable energy, healthcare and information science. In the latter case, the intrinsic quantum nature of the electronic, nuclear and spin degrees of freedom in molecules offers intriguing new possibilities to advance the emerging field of quantum information science. In this Perspective, which resulted from discussions by the co-authors at a US Department of Energy workshop held in November 2018, we discuss how chemical systems and reactions can impact quantum computing, communication and sensing. Hierarchical molecular design and synthesis, from small molecules to supramolecular assemblies, combined with new spectroscopic probes of quantum coherence and theoretical modelling of complex systems, offer a broad range of possibilities to realize practical quantum information science applications. Open Access articles citing this article. • • Gheorghe Taran • , Eufemio Moreno-Pineda • … Wolfgang Wernsdorfer Nature Communications ...

Decoherence of a two-qubit system is studied when each qubit interacts with a Markovian environment in an indefinite way. It is assumed that which environment of the two interacts with each qubit is determined by a controller qubit. This leads to indefiniteness of the environments. When information conveyed by the controller qubit is discarded, the quantum channel of the two qubits is given by a statistical mixture of the two Markovian channels. When appropriate projective measurement is performed on the controller qubit, it is found that the indefiniteness of the two environments significantly affects the output state of the two qubits. Once a specific measurement outcome is obtained, the output state becomes the Bell singlet state even if an initial state of the two qubit has no quantum correlation. Even when the measurement yields the other outcome, the entanglement, the Bell-inequality violation and the quantum discord can be enhanced. • Previous article in issue • Next article in issue • About ScienceDirect • Remote access • Shopping cart • Advertise • Contact and support • Terms and conditions • Privacy policy We use cookies to help provide and enhance our service and tailor content and ads. By continuing you agree to the use of cookies. Copyright © 2023 Elsevier B.V. or its licensors or contributors. ScienceDirect® is a registered trademark of Elsevier B.V. ScienceDirect® is a registered trademark of Elsevier B.V.

In this article Just as bits are the fundamental object of information in classical computing, qubits (quantum bits) are the fundamental object of information in quantum computing. To understand this correspondence, this article looks at the simplest example: a single qubit. Representing a qubit While a bit, or binary digit, can have a value either $0$ or $1$, a qubit can have a value that is either $0$, $1$ or a quantum superposition of $0$ and $1$. The state of a single qubit can be described by a two-dimensional column vector of unit norm, that is, the magnitude squared of its entries must sum to $1$. This vector, called the quantum state vector, holds all the information needed to describe the one-qubit quantum system just as a single bit holds all of the information needed to describe the state of a binary variable. Any two-dimensional column vector of real or complex numbers with norm $1$ represents a possible quantum state held by a qubit. Thus $\begin R_x(\beta)R_z(\gamma)R_x(\delta)$. Thus $R_z(\theta)$ and $H$ also form a universal gate set although it is not a discrete set because $\theta$ can take any value. For this reason, and due to applications in quantum simulation, such continuous gates are crucial for quantum computation, especially at the quantum algorithm design level. To achieve fault-tolerant hardware implementation, they will ultimately be compiled into discrete gate sequences that closely approximate these rotations.

Decoherence of a two-qubit system is studied when each qubit interacts with a Markovian environment in an indefinite way. It is assumed that which environment of the two interacts with each qubit is determined by a controller qubit. This leads to indefiniteness of the environments. When information conveyed by the controller qubit is discarded, the quantum channel of the two qubits is given by a statistical mixture of the two Markovian channels. When appropriate projective measurement is performed on the controller qubit, it is found that the indefiniteness of the two environments significantly affects the output state of the two qubits. Once a specific measurement outcome is obtained, the output state becomes the Bell singlet state even if an initial state of the two qubit has no quantum correlation. Even when the measurement yields the other outcome, the entanglement, the Bell-inequality violation and the quantum discord can be enhanced. • Previous article in issue • Next article in issue • About ScienceDirect • Remote access • Shopping cart • Advertise • Contact and support • Terms and conditions • Privacy policy We use cookies to help provide and enhance our service and tailor content and ads. By continuing you agree to the use of cookies. Copyright © 2023 Elsevier B.V. or its licensors or contributors. ScienceDirect® is a registered trademark of Elsevier B.V. ScienceDirect® is a registered trademark of Elsevier B.V.

• Perspective • 07 July 2020 Exploiting chemistry and molecular systems for quantum information science • ORCID: orcid.org/0000-0003-2920-5440 • • ORCID: orcid.org/0000-0003-0945-1492 • • • • • ORCID: orcid.org/0000-0002-2579-8835 • • • ORCID: orcid.org/0000-0002-1479-3318 • • • • ORCID: orcid.org/0000-0003-4255-9550 • … • Show authors Nature Reviews Chemistry volume 4, pages 490–504 ( 2020) The power of chemistry to prepare new molecules and materials has driven the quest for new approaches to solve problems having global societal impact, such as in renewable energy, healthcare and information science. In the latter case, the intrinsic quantum nature of the electronic, nuclear and spin degrees of freedom in molecules offers intriguing new possibilities to advance the emerging field of quantum information science. In this Perspective, which resulted from discussions by the co-authors at a US Department of Energy workshop held in November 2018, we discuss how chemical systems and reactions can impact quantum computing, communication and sensing. Hierarchical molecular design and synthesis, from small molecules to supramolecular assemblies, combined with new spectroscopic probes of quantum coherence and theoretical modelling of complex systems, offer a broad range of possibilities to realize practical quantum information science applications. Open Access articles citing this article. • • Gheorghe Taran • , Eufemio Moreno-Pineda • … Wolfgang Wernsdorfer Nature Communications ...

Most works on open quantum systems generally focus on the reduced physical system by tracing out the environment degrees of freedom. Here we show that the qubit distributions with the environment are essential for a thorough analysis and demonstrate that the way that quantum correlations are distributed in a quantum register is constrained by the way in which each subsystem gets correlated with the environment. For a two-qubit system coupled to a common dissipative environment , we show how to optimise interqubit correlations and entanglement via a quantification of the qubit-environment information flow, in a process that, perhaps surprisingly, does not rely on the knowledge of the state of the environment. To illustrate our findings, we consider an optically-driven bipartite interacting qubit AB system under the action of . By tailoring the light-matter interaction, a relationship between the qubits early stage disentanglement and the qubit-environment entanglement distribution is found. We also show that, under suitable initial conditions, the qubits energy asymmetry allows the identification of physical scenarios whereby qubit-qubit entanglement minima coincide with the extrema of the and entanglement oscillations. The quantum properties of physical systems have been studied for many years as crucial resources for quantum processing tasks and quantum information protocols Many works devoted to the study of entanglement and correlations dynamics in open quantum systems ...