X-states of a qubit pair of double classicality
A special class of states of 2-qubits which are simultaneously separable and have positive semidefinite Wigner functions is described.
quant-ph↗
arXiv subjects
Dimitar Mladenov
Publications and source records attributed to Dimitar Mladenov.
Towards parameterizing the entanglement body of a qubit pair
A method allowing to increase a computational efficiency of evaluation of non-local characteristics of a pair of qubits is described. The method is based on the construction of coordinates on a generic section of 2-qubit's entanglement space $\mathcal{E}_{2\times2}$ represented as the direct product of an ordered 3-dimensional simplex and the double coset $\mathrm{SU(2)}\times\mathrm{SU(2)}{\backslash} {\mathrm{SU(4)}}/ \mathrm{T^3}\,.$ Within this framework, the subset $\mathcal{SE}_{2\times2} \subset\mathcal{E}_{2\times2}$ corresponding to the rank-4 separable 2-qubit states is described as a semialgebraic variety given by a system of 3rd and 4th order polynomial inequalities in eigenvalues of the density matrix, whereas the polynomials coefficients are trigonometric functions defined over a direct product of two regular octahedra.
quant-ph↗
One other parameterization of SU(4) group
We propose a special decomposition of the Lie $\mathfrak{su}(4)$ algebra into the direct sum of orthogonal subspaces, $\mathfrak{su}(4)=\mathfrak{k}\oplus\mathfrak{a}\oplus\mathfrak{a}^\prime\oplus\mathfrak{t}\,,$ with $\mathfrak{k}=\mathfrak{su}(2)\oplus\mathfrak{su}(2)$ and a triplet of 3-dimensional Abelian subalgebras $(\mathfrak{a}, \mathfrak{a}^{\prime}, \mathfrak{t})\,,$ such that the exponential mapping of a neighbourhood of the $0\in \mathfrak{su}(4)$ into a neighbourhood of the identity of the Lie group provides the following factorization of an element of $SU(4)$ \[ g = k\,a\,t\,, \] where $k \in \exp{(\mathfrak{k})} = SU(2)\times SU(2) \subset SU(4)\,,$ the diagonal matrix $t$ stands for an element from the maximal torus $T^3=\exp{(\mathfrak{t})},$ and the factor $a=\exp{(\mathfrak{a})}\exp{(\mathfrak{a}^\prime)}$ corresponds to a point in the double coset $SU(2)\times SU(2)\backslash SU(4)/T^3.$ Analyzing the uniqueness of the inverse of the above exponential mappings, we establish a logarithmic coordinate chart of the $SU(4)$ group manifold comprising 6 coordinates on the embedded manifold $ SU(2)\times SU(2) \subset SU(4)$ and 9 coordinates on three copies of the regular octahedron with the edge length $2\pi\sqrt{2}\,$.
math.GR↗
First Direct Observation of Collider Neutrinos with FASER at the LHC
We report the first direct observation of neutrino interactions at a particle collider experiment. Neutrino candidate events are identified in a 13.6 TeV center-of-mass energy $pp$ collision data set of 35.4 fb${}^{-1}$ using the active electronic components of the FASER detector at the Large Hadron Collider. The candidates are required to have a track propagating through the entire length of the FASER detector and be consistent with a muon neutrino charged-current interaction. We infer $153^{+12}_{-13}$ neutrino interactions with a significance of 16 standard deviations above the background-only hypothesis. These events are consistent with the characteristics expected from neutrino interactions in terms of secondary particle production and spatial distribution, and they imply the observation of both neutrinos and anti-neutrinos with an incident neutrino energy of significantly above 200 GeV.
hep-ex↗
The FASER Detector
FASER, the ForwArd Search ExpeRiment, is an experiment dedicated to searching for light, extremely weakly-interacting particles at CERN's Large Hadron Collider (LHC). Such particles may be produced in the very forward direction of the LHC's high-energy collisions and then decay to visible particles inside the FASER detector, which is placed 480 m downstream of the ATLAS interaction point, aligned with the beam collisions axis. FASER also includes a sub-detector, FASER$\nu$, designed to detect neutrinos produced in the LHC collisions and to study their properties. In this paper, each component of the FASER detector is described in detail, as well as the installation of the experiment system and its commissioning using cosmic-rays collected in September 2021 and during the LHC pilot beam test carried out in October 2021. FASER will start taking LHC collision data in 2022, and will run throughout LHC Run 3.
physics.ins-det↗
The tracking detector of the FASER experiment
FASER is a new experiment designed to search for new light weakly-interacting long-lived particles (LLPs) and study high-energy neutrino interactions in the very forward region of the LHC collisions at CERN. The experimental apparatus is situated 480 m downstream of the ATLAS interaction-point aligned with the beam collision axis. The FASER detector includes four identical tracker stations constructed from silicon microstrip detectors. Three of the tracker stations form a tracking spectrometer, and enable FASER to detect the decay products of LLPs decaying inside the apparatus, whereas the fourth station is used for the neutrino analysis. The spectrometer has been installed in the LHC complex since March 2021, while the fourth station is not yet installed. FASER will start physics data taking when the LHC resumes operation in early 2022. This paper describes the design, construction and testing of the tracking spectrometer, including the associated components such as the mechanics, readout electronics, power supplies and cooling system.
physics.ins-det↗
The trigger and data acquisition system of the FASER experiment
The FASER experiment is a new small and inexpensive experiment that is placed 480 meters downstream of the ATLAS experiment at the CERN LHC. FASER is designed to capture decays of new long-lived particles, produced outside of the ATLAS detector acceptance. These rare particles can decay in the FASER detector together with about 500-1000 Hz of other particles originating from the ATLAS interaction point. A very high efficiency trigger and data acquisition system is required to ensure that the physics events of interest will be recorded. This paper describes the trigger and data acquisition system of the FASER experiment and presents performance results of the system acquired during initial commissioning.
physics.ins-det↗
Parameterizing Qudit States
Quantum systems with a finite number of states at all times have been a primary element of many physical models in nuclear and elementary particle physics, as well as in condensed matter physics. Today, however, due to a practical demand in the area of developing quantum technologies, a whole set of novel tasks for improving our understanding of the structure of finite-dimensional quantum systems has appeared. In the present article we will concentrate on one aspect of such studies related to the problem of explicit parameterization of state space of an $N$-level quantum system. More precisely, we will discuss the problem of a practical description of the unitary $SU(N)$-invariant counterpart of the $N$-level state space $\mathfrak{P}_N$, i.e., the unitary orbit space $\mathfrak{P}_N/SU(N)$. It will be demonstrated that the combination of well-known methods of the polynomial invariant theory and convex geometry provides useful parameterization for the elements of $\mathfrak{P}_N/SU(N)$. To illustrate the general situation, a detailed description of $\mathfrak{P}_N/SU(N)$ for low-level systems: qubit $(N=2)\,,$ qutrit $(N=3)\,,$ quatrit $(N=4)\,$ - will be given.
quant-ph↗
First neutrino interaction candidates at the LHC
FASER$\nu$ at the CERN Large Hadron Collider (LHC) is designed to directly detect collider neutrinos for the first time and study their cross sections at TeV energies, where no such measurements currently exist. In 2018, a pilot detector employing emulsion films was installed in the far-forward region of ATLAS, 480 m from the interaction point, and collected 12.2 fb$^{-1}$ of proton-proton collision data at a center-of-mass energy of 13 TeV. We describe the analysis of this pilot run data and the observation of the first neutrino interaction candidates at the LHC. This milestone paves the way for high-energy neutrino measurements at current and future colliders.
hep-ex↗
Technical Proposal: FASERnu
FASERnu is a proposed small and inexpensive emulsion detector designed to detect collider neutrinos for the first time and study their properties. FASERnu will be located directly in front of FASER, 480 m from the ATLAS interaction point along the beam collision axis in the unused service tunnel TI12. From 2021-23 during Run 3 of the 14 TeV LHC, roughly 1,300 electron neutrinos, 20,000 muon neutrinos, and 20 tau neutrinos will interact in FASERnu with TeV-scale energies. With the ability to observe these interactions, reconstruct their energies, and distinguish flavors, FASERnu will probe the production, propagation, and interactions of neutrinos at the highest human-made energies ever recorded. The FASERnu detector will be composed of 1000 emulsion layers interleaved with tungsten plates. The total volume of the emulsion and tungsten is 25cm x 25cm x 1.35m, and the tungsten target mass is 1.2 tonnes. From 2021-23, 7 sets of emulsion layers will be installed, with replacement roughly every 20-50 1/fb in planned Technical Stops. In this document, we summarize FASERnu's physics goals and discuss the estimates of neutrino flux and interaction rates. We then describe the FASERnu detector in detail, including plans for assembly, transport, installation, and emulsion replacement, and procedures for emulsion readout and analyzing the data. We close with cost estimates for the detector components and infrastructure work and a timeline for the experiment.
physics.ins-det↗
A strong laser impact on spin precession of a charged particle in the semi-relativistic interaction regime
In the present note new effects concerned the dynamics of a charged spin-1/2 particle in a strong monochromatic plane wave background are discussed beyond the conventional dipole approximation. Namely using the semiclassical approach in the semi-relativistic regime it is shown that the magnetic forces associated with the laser field have been retained and alter the spin evolution appreciably.
quant-ph↗
Local invariants for mixed qubit-qutrit states
In the present paper few steps are undertaken towards the description of the qubit-qutrit pair - quantum bipartite system composed of two and three level subsystems. The computational difficulties with the construction of the local unitary polynomial invariants are discussed. Calculations of the Molien functions and Poincare series for the qubit-qubit and qubit-qutrit local unitary invariants are outlined and compared with the known results. The requirement of positive semi-definiteness of the density operator is formulated explicitly as a set of inequalities in five Casimir invariants of the algebra su(6).
quant-ph↗
On application of involutivity analysis of differential equations to constrained dynamical systems
A brief sketch of computer methods of involutivity analysis of differential equations is presented in context of its application to study degenerate Lagrangian systems. We exemplify the approach by a detailed consideration of a finite-dimensional model, the so-called light-cone SU(2) Yang-Mills mechanics. All algorithms are realized in computer algebra system Maple.
hep-th↗