EDITORS' SUGGESTION
Microwave-free magnetometry with N- centers has emerged as a complementary method to traditional techniques when the use of microwaves is impractical, particularly in applications involving metals and biological samples. Integration of this method with imaging capabilities offers the potential for nondestructive probing in a 2D spatial plane, while also capturing temporal dynamics within existing technological constraints. It is evident that the limits of sensitivity have not been fully realized, and improvements may be achieved via faster specialized cameras and advanced color-center fabrication.
Joseph Shaji Rebeirro et al.
Phys. Rev. Applied 21, 044039 (2024)
PERSPECTIVE
Dynamic beamforming is critical in applications such as radar detection, holographic imaging, and reconfigurable intelligent surfaces (RIS). This Perspective reviews a revolutionary and economical technique to achieve dynamic beamforming, utilizing the moiré pattern formed by twisted stacked metasurfaces. Research here faces challenges such as far-field calculations and the inverse design of specific radiation patterns, due to our limited understanding of the complex mode coupling between the moiré pattern and the metallic back plate. The authors outline potential solutions and project the future applications and research directions for the reflective moiré metasurface.
Shuo Liu and Tie Jun Cui
Phys. Rev. Applied 21, 040502 (2024)
EDITORS' SUGGESTION
The ultrafast all-optical control of magnetization without relying on heat is promising for magnetic recording technology. While the magnetization switching between two stable bit states does not require control over light polarization, photomagnetic toggling of magnetization (equivalent to the XOR logic operation) can be achieved. This study probes the efficiency of a back-switching scenario between two stable bit states, using a pair of femtosecond laser pulses with either the same or orthogonal orientations of linear polarization. Such a nonthermal toggle regime not only can provide recording at rates up to 50 GHz, but also can perform basic logic operations.
T. Zalewski, L. Nowak, and A. Stupakiewicz
Phys. Rev. Applied 21, 044026 (2024)
EDITORS' SUGGESTION
Spin pumping can generate spin current by driving a magnetic system into resonance, a phenomenon that can be electrically detected via the inverse spin Hall effect. However, the efficiency of spin current generation has remained limited, compared to that of spin-to-charge conversion. This work systematically demonstrates an innovative technique for electrically probing propagating spin waves and creating spin current with high efficiency, mediated by flat-band magnons excited by broad wave vectors. These findings lay a promising foundation for further experiments with propagating spin waves.
Jinlong Wang et al.
Phys. Rev. Applied 21, 044024 (2024)
EDITORS' SUGGESTION
The development of gain-driven polaritons offers a fresh approach to enhancing solid-state microwave sources and amplifiers, apart from the traditional concept of the maser. Despite their potential, these polaritons are governed by intricate dynamics that remain largely unexplored, impeding practical applications. The authors employ time-domain measurements to investigate the transient response of gain-driven polaritons, revealing distinct dynamical behaviors: damping, zero damping, and antidamping. This insight could impact the engineering of ultrafast polaritonic devices tailored for coherent microwave and optical applications.
Y.S. Gui and C.-M. Hu
Phys. Rev. Applied 21, 044023 (2024)
PERSPECTIVE
While public key cryptography enables the Internet to carry secure communications for billions of people every day, this critical technology is not infallible. It is well known that the Internet needs to transition to new “post-quantum” cryptosystems, to protect against the possibility of future cryptanalysis using quantum computers. This Perspective suggests that there is a broader scope for using quantum technologies to enhance cybersecurity, including fundamentally different approaches to constructing hardware security modules, to protect the secret keys that are the linchpin of cryptography on the Internet.
Yi-Kai Liu and Dustin Moody
Phys. Rev. Applied 21, 040501 (2024)
LETTER
Reconstructing the effective equation of motion for the time evolution of a subset of degrees of freedom of a larger system remains a problem of interest in quantum physics. Many methods have been developed, but they either rely on an ad hoc ansatz, demand data that is not experimentally accessible, or lack physical interpretability. The authors employ machine-learning methods to infer the effective dynamical generator from a noisy, finite set of local measurements. Their method yields interpretable results that may be used to infer noise models on quantum simulators, or to study thermalization dynamics in quantum many-body systems.
Giovanni Cemin et al.
Phys. Rev. Applied 21, L041001 (2024)
EDITORS' SUGGESTION
Recent probabilistic computing frameworks have used a microprocessors-in-the-loop approach to sensing output signals and applying control voltages. Here the authors study the dynamics of an analog, two-spin Ising computer built from superparamagnetic tunnel junctions (SMTJs). The op-amp-based circuit features polarity selection and programmable gain, allowing both positive and negative coupling and the performance of simulated annealing. While scaling of this design requires only trivial circuit modifications, large networks of spins would require SMTJs with enhanced properties, suggesting that a co-design approach between devices, architectures, and algorithms is necessary.
Sidra Gibeault et al.
Phys. Rev. Applied 21, 034064 (2024)
EDITORS' SUGGESTION
Unbiased sources of true randomness are crucial for the next generation of encryption applications and stochastic computing in various fields, yet achieving such randomness without bias has remained technically challenging. This study introduces an innovative hardware approach, utilizing the intrinsic balance of phase noise in a spintronic nano-oscillator synchronized at twice its natural frequency to overcome bias in random bitstream generation at room temperature. The method generates truly random bitstreams with efficiency and reliability that is expected to significantly impact cybersecurity, advanced computing, and more.
Nhat-Tan Phan et al.
Phys. Rev. Applied 21, 034063 (2024)
