When noise becomes the signal
Related Articles
Noise causes cardiovascular disease: it’s time to act
Chronic transportation noise is an environmental stressor affecting a substantial portion of the population. The World Health Organization (WHO) and various studies have established associations between transportation noise and cardiovascular disease (CVD), such as myocardial infarction, stroke, heart failure, and arrhythmia. The WHO Environmental Noise Guidelines and recent reviews confirm a heightened risk of cardiovascular incidents with increasing transportation noise levels.
Comparative analysis of nanomechanical resonators: sensitivity, response time, and practical considerations in photothermal sensing
Nanomechanical photothermal sensing has significantly advanced single-molecule/particle microscopy and spectroscopy, and infrared detection. In this approach, the nanomechanical resonator detects shifts in resonant frequency due to photothermal heating. However, the relationship between photothermal sensitivity, response time, and resonator design has not been fully explored. This paper compares three resonator types – strings, drumheads, and trampolines – to explore this relationship. Through theoretical modeling, experimental validation, and finite element method simulations, we find that strings offer the highest sensitivity (with a noise equivalent power of 280 fW/Hz1/2 for strings made of silicon nitride), while drumheads exhibit the fastest thermal response. The study reveals that photothermal sensitivity correlates with the average temperature rise and not the peak temperature. Finally, the impact of photothermal back-action is discussed, which can be a major source of frequency instability. This work clarifies the performance differences and limits among resonator designs and guides the development of advanced nanomechanical photothermal sensors, benefiting a wide range of applications.
Dynamic thermalization on noisy quantum hardware
Emulating thermal observables on a digital quantum computer is essential for quantum simulation of many-body physics. However, thermalization typically requires a large system size due to incorporating a thermal bath, whilst limited resources of near-term digital quantum processors allow for simulating relatively small systems. We show that thermal observables and fluctuations may be obtained for a small closed system without a thermal bath. Thermal observables occur upon classically averaging quantum mechanical observables over randomized variants of their time evolution that run independently on a digital quantum processor. Using an IBM quantum computer, we experimentally find thermal occupation probabilities with finite positive and negative temperatures defined by the initial state’s energy. Averaging over random evolutions facilitates error mitigation, with the noise contributing to the temperature in the simulated observables. This result fosters probing the dynamical emergence of equilibrium properties of matter at finite temperatures on noisy intermediate-scale quantum hardware.
Dual wavelength Brillouin laser terahertz source stabilized to carbonyl sulfide rotational transition
Optical-based terahertz sources are important for many burgeoning scientific and technological applications. Among such applications is precision spectroscopy of molecules, which exhibit rotational transitions at terahertz frequencies. Stemming from precision spectroscopy is frequency discrimination (a core technology in atomic clocks) and stabilization of terahertz sources. Because many molecular species exist in the gas phase at room temperature, their transitions are prime candidates for practical terahertz frequency references. We demonstrate the stabilization of a low phase-noise, dual-wavelength Brillouin laser (DWBL) terahertz oscillator to a rotational transition of carbonyl sulfide (OCS). We achieve an instability of (1.2times 1{0}^{-12}/sqrt{tau }), where τ is the averaging time in seconds. The signal-to-noise ratio and intermodulation limitations of the experiment are also discussed. We thus demonstrate a highly stable and spectrally pure terahertz frequency source. Our presented architecture will likely benefit metrology, spectroscopy, precision terahertz studies, and beyond.
Signal theory based encryption of faster-than-Nyquist signals for fiber and wireless transmission
New applications such as the Internet of Things, autonomous driving, Industry X.0 and many more will transmit sensitive information via fibers and over the air with envisioned data rates beyond terabits per second. Therefore, the encryption has to be simple, fast and spectrally efficient, so that the power consumption and latency are low and the scarce bandwidth is not wasted. Various encryption schemes, based on mathematical algorithms, quantum theory, chaos communication or spectral spreading below the noise level have been explored. Besides power, spectral efficiency and latency, most of these approaches face additional challenges such as limited data rates, compatibility issues with communication standards and integration. Here, we propose a signal theory based method that enables the encryption of super-signals with bandwidths of hundreds of gigahertz without any additional bandwidth. In proof-of-concept experiments we demonstrate the encryption of a 270 GBd faster than Nyquist super-signal in a 252.4 GHz bandwidth. The encryption is simple, fast and power efficient, and offers a solution for secure data transmission in existing and future communication networks.
Responses