Quantum Enhancement in Dark Matter Detection with Quantum Computation

We propose a novel method to significantly enhance the signal rate in the qubit-based dark matter detection experiments with the help of quantum interference. Various quantum sensors possess ideal properties for detecting wave-like dark matter, and qubits, commonly employed in quantum computers, are excellent candidates for dark matter detectors. We demonstrate that, by designing an appropriate quantum circuit to manipulate the qubits, the signal rate scales proportionally to $n_{\rm q}^2$, with $n_{\rm q}$ being the number of sensor qubits, rather than linearly with $n_{\rm q}$. Consequently, in the dark matter detection with a substantial number of sensor qubits, a significant increase in the signal rate can be expected. We provide a specific example of a quantum circuit that achieves this enhancement by coherently combining the phase evolution in each individual qubit due to its interaction with dark matter. We also demonstrate that the circuit is fault tolerant to de-phasing noises, a critical quantum noise source in quantum computers. The enhancement mechanism proposed here is applicable to various modalities for quantum computers, provided that the quantum operations relevant to enhancing the dark matter signal can be applied to these devices.Comment: 7 pages, 2 figure

Detection of hidden photon dark matter using the direct excitation of transmon qubits

We propose a novel dark matter detection method utilizing the excitation of superconducting transmon qubits. Assuming the hidden photon dark matter of a mass of $O(10)\ \mu{\rm eV}$, the classical wave-matter oscillation induces an effective ac electric field via the small kinetic mixing with the ordinary photon. This serves as a coherent drive field for a qubit when it is resonant, evolving it from the ground state towards the first-excited state. We evaluate the rate of such evolution and observable excitations in the measurements, as well as the search sensitivity to the hidden photon dark matter. For a selected mass, one can reach $\epsilon \sim 10^{-12}-10^{-14}$ (where $\epsilon$ is the kinetic mixing parameter of the hidden photon) with a single standard transmon qubit. A simple extension to the frequency-tunable SQUID-based transmon enables the mass scan to cover the whole $4-40\ \mu{\rm eV}$ ($1-10$ GHz) range within a reasonable length of run time. The sensitivity scalability along the number of the qubits also makes it a promising platform in accord to the rapid evolution of the superconducting quantum computer technology.Comment: 7 pages, 1 figure, published versio

Observing Axion Emission from Supernova with Collider Detectors

We consider a possibility to observe the axion emission from a nearby supernova (SN) in the future, which can be known in advance by the pre-SN alert system, by collider detectors like the LHC detectors (i.e., the ATLAS and the CMS) and the ILC detectors (i.e., the ILD and SiD). The axion from the SN can be converted to the photon by the strong magnetic field in the detector and the photon can be detected by electromagnetic calorimeter. We estimate the numbers of signal and background events due to a nearby SN and show that the number of signal may be sizable. The axion emission from a nearby SN may be observed if, at the time of the SN, the beam is stopped and the detector operation is switched to the one for the SN axion search.Comment: 21 pages, 4 figures, 2 tables; v2: corrected typos, added footnote about signal & background time curve, emphasized the result, conclusions unchange

Theoretical investigation about the optical characterization of cone-shaped pin-Si nanowire for top cell application

Cone-shaped semiconductor silicon nanowires (CS-Si-NWs) grown in vapor liquid solid mode are promising for the fabrication of low-cost high-performance solar cells because of their low processing cost and lower use of Si materials, as compared to planar devices. In this article, the effect of injected charge carriers on the refractive indices and extinction coefficient values in a cone-shaped pin Si NW (CS-pin-Si NW) were considered. Then, the influence of top diameters and periods on the optical absorption was investigated using a finite difference time-domain (FDTD) modeling method. The absorption increased when we decreased the period from 300 to 150 nm for a light wave with a wavelength of 700 nm. However, in the case of incident light at a wavelength of 500 nm, the absorption significantly increased by up to 100% and was found to be independent of the period. On the other hand, we varied the period and the top diameter of the NWs with a fixed bottom diameter. In this case, we found that the period did not significantly affect the absorption value. A high value of the short circuit current density of 19.5 mA/cm2 was found in the case of NWs with a top diameter of 110 nm and a period of 150 nm. Combined with the analysis of the ultimate photocurrents, an optimum geometric structure with a top diameter of 70 nm and a period of 150 nm for a CS-pin-Si NW-based top cell for tandem solar cell applications was proposed