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1. Dark Matter Axion Search with HAYSTAC Phase II

   https://doi.org/10.1103/PhysRevLett.134.151006  

   Bai, Xiran; Jewell, M J; Echevers, J; van_Bibber, K; Droster, A; Esmat, Maryam H; Ghosh, Sumita; Graham, Eleanor; Jackson, H; Laffan, Claire; et al (April 2025, Physical Review Letters)

   This Letter reports new results from the HAYSTAC experiment’s search for dark matter axions in our galactic halo. It represents the widest search to date that utilizes squeezing to realize subquantum limited noise. The new results cover $1.71\mathrm{\mu }\mathrm{eV}$of newly scanned parameter space in the mass ranges $17.28–18.44\mathrm{\mu }\mathrm{eV}$and $18.71–19.46\mathrm{\mu }\mathrm{eV}$. No statistically significant evidence of an axion signal was observed, excluding couplings $\left|g_{\gamma }\right|\ge 2.75\times \left|g_{\gamma }^{\mathrm{KSVZ}}\right|$and $\left|g_{\gamma }\right|\ge 2.96\times \left|g_{\gamma }^{\mathrm{KSVZ}}\right|$at the 90% confidence level over the respective region. By combining this data with previously published results using HAYSTAC’s squeezed state receiver, a total of $2.27\mathrm{\mu }\mathrm{eV}$of parameter space has now been scanned between $16.96–19.46\mathrm{\mu }\mathrm{eV}$ $\mu \mathrm{eV}$, excluding $\left|g_{\gamma }\right|\ge 2.86\times \left|g_{\gamma }^{\mathrm{KSVZ}}\right|$at the 90% confidence level. These results demonstrate the squeezed state receiver’s ability to probe axion models over a significant mass range while achieving a scan rate enhancement relative to a quantum-limited experiment. Published by the American Physical Society2025 

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2. Quantum group intertwiner space from quantum curved tetrahedron

   https://doi.org/10.1088/1361-6382/ad5f71  

   Han, Muxin; Hsiao, Chen-Hung; Pan, Qiaoyin (July 2024, Classical and Quantum Gravity)

   Abstract In this paper, we develop a quantum theory of homogeneously curved tetrahedron geometry, by applying the combinatorial quantization to the phase space of tetrahedron shapes defined in Haggardet al(2016Ann. Henri Poincaré172001–48). Our method is based on the relation between this phase space and the moduli space of SU(2) flat connections on a 4-punctured sphere. The quantization results in the physical Hilbert space as the solution of the quantum closure constraint, which quantizes the classical closure condition $M_4{M}_3{M}_2{M}_1=1$, $M_{\nu }\in \mathrm{SU}\left(2\right)$, for the homogeneously curved tetrahedron. The quantum group $U_q\left(\mathfrak{su}\right(2\left)\right)$emerges as the gauge symmetry of a quantum tetrahedron. The physical Hilbert space of the quantum tetrahedron coincides with the Hilbert space of 4-valent intertwiners of $U_q\left(\mathfrak{su}\right(2\left)\right)$. In addition, we define the area operators quantizing the face areas of the tetrahedron and compute the spectrum. The resulting spectrum is consistent with the usual Loop-Quantum-Gravity area spectrum in the large spin regime but is different for small spins. This work closely relates to 3+1 dimensional Loop Quantum Gravity in presence of cosmological constant and provides a justification for the emergence of quantum group in the theory. 

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3. Quantum circuits for toric code and X-cube fracton model

   https://doi.org/10.22331/q-2024-03-13-1276  

   Chen, Penghua; Yan, Bowen; Cui, Shawn X (March 2024, Quantum)

   We propose a systematic and efficient quantum circuit composed solely of Clifford gates for simulating the ground state of the surface code model. This approach yields the ground state of the toric code in $\lceil 2L+2+lo{g}_2\left(d\right)+\frac{L}{2d}\rceil$time steps, where $L$refers to the system size and $d$represents the maximum distance to constrain the application of the CNOT gates. Our algorithm reformulates the problem into a purely geometric one, facilitating its extension to attain the ground state of certain 3D topological phases, such as the 3D toric model in $3L+8$steps and the X-cube fracton model in $12L+11$steps. Furthermore, we introduce a gluing method involving measurements, enabling our technique to attain the ground state of the 2D toric code on an arbitrary planar lattice and paving the way to more intricate 3D topological phases. 

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4. First Measurement of the $\left|t\right|$ Dependence of Incoherent $J/\psi$ Photonuclear Production

   https://doi.org/10.1103/PhysRevLett.132.162302  

   Acharya, S; Adamová, D; Adler, A; Aglieri_Rinella, G; Agnello, M; Agrawal, N; Ahammed, Z; Ahmad, S; Ahn, S U; Ahuja, I; et al (April 2024, Physical Review Letters)

   The first measurement of the cross section for incoherent photonuclear production of $J/\psi$vector mesons as a function of the Mandelstam $\left|t\right|$variable is presented. The measurement was carried out with the ALICE detector at midrapidity, $\left|y\right|<0.8$, using ultraperipheral collisions of Pb nuclei at a center-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$. This rapidity interval corresponds to a Bjorken- $x$range $\left(0.3–1.4\right)\times {10}^{-3}$. Cross sections are given in five $\left|t\right|$intervals in the range $0.04<\left|t\right|<1{\mathrm{GeV}}^2$and compared to the predictions by different models. Models that ignore quantum fluctuations of the gluon density in the colliding hadron predict a $\left|t\right|$dependence of the cross section much steeper than in data. The inclusion of such fluctuations in the same models provides a better description of the data. © 2024 CERN, for the ALICE Collaboration2024CERN 

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5. Spacetime-Efficient Low-Depth Quantum State Preparation with Applications

   https://doi.org/10.22331/q-2024-02-15-1257  

   Gui, Kaiwen; Dalzell, Alexander M.; Achille, Alessandro; Suchara, Martin; Chong, Frederic T. (February 2024, Quantum)

   We propose a novel deterministic method for preparing arbitrary quantum states. When our protocol is compiled into CNOT and arbitrary single-qubit gates, it prepares an $N$-dimensional state in depth $O(\log (N\left)\right)$and $\text{spacetime allocation}$(a metric that accounts for the fact that oftentimes some ancilla qubits need not be active for the entire circuit) $O\left(N\right)$, which are both optimal. When compiled into the $\left\{\mathrm{H},\mathrm{S},\mathrm{T},\mathrm{C}\mathrm{N}\mathrm{O}\mathrm{T}\right\}$gate set, we show that it requires asymptotically fewer quantum resources than previous methods. Specifically, it prepares an arbitrary state up to error $ϵ$with optimal depth of $O(\log (N)+\log (1/ϵ\left)\right)$and spacetime allocation $O(N\log (\log \left(N\right)/ϵ\left)\right)$, improving over $O(\log (N)\log (\log \left(N\right)/ϵ\left)\right)$and $O(N\log (N/ϵ\left)\right)$, respectively. We illustrate how the reduced spacetime allocation of our protocol enables rapid preparation of many disjoint states with only constant-factor ancilla overhead – $O\left(N\right)$ancilla qubits are reused efficiently to prepare a product state of $w$ $N$-dimensional states in depth $O(w+\log (N\left)\right)$rather than $O(w\log (N\left)\right)$, achieving effectively constant depth per state. We highlight several applications where this ability would be useful, including quantum machine learning, Hamiltonian simulation, and solving linear systems of equations. We provide quantum circuit descriptions of our protocol, detailed pseudocode, and gate-level implementation examples using Braket. 

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