Quantum vs. Classical Sensing: Differences Explained

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Discover the difference between quantum sensing and classical sensing, explore real-world applications, and learn why this technology matters.

Quantum Sensing vs. Classical Sensing: What's the Difference and Why It Matters

Some signals are simply too small for conventional sensors to detect. The magnetic fields generated by brain activity, minute variations in gravity, and tiny distortions in spacetime all present measurement challenges at the limits of classical sensing. Quantum sensors can push beyond some of those limits by using properties of atoms, photons, and other quantum systems to detect extremely small changes with remarkable sensitivity and precision.

That capability has implications far beyond the laboratory. More sensitive measurements could improve medical imaging, enable navigation without global positioning systems (GPS), reveal what lies beneath Earth’s surface, and help scientists detect events across the universe.

This post will explore the fundamentals of quantum sensing, ways in which quantum and classical sensing differ, and some of the applications that demonstrate the potential of quantum measurement.

Key Takeaways

Quantum sensors use properties of quantum mechanics to measure physical quantities in ways that would be impossible with classical physics alone¹
Quantum sensing can reduce measurement uncertainty below the standard quantum limit, approaching the more precise Heisenberg limit²
Quantum principles are already at work in established technologies such as atomic clocks and magnetic resonance imaging (MRI)¹
Emerging quantum sensing applications could expand capabilities in healthcare, geology, navigation, infrastructure monitoring, and fundamental physics³
Quantum techniques such as squeezed light are helping observatories reduce noise and improve the detection of gravitational waves⁴

Understanding the Fundamentals of Quantum Sensing

Quantum sensing takes advantage of the distinctive ways matter behaves at the molecular, atomic, and subatomic scales. A quantum sensor uses properties of quantum mechanics to measure physical quantities in ways that traditional instruments cannot.¹ Phenomena such as superposition and entanglement can enable exceptionally precise measurements of gravity, temperature, and electric and magnetic fields.⁵

Quantum sensors can also offer the important advantage of consistency. Sensors based on atoms can produce measurements that do not require calibration against an external standard because atoms of the same element are fundamentally identical.¹ That inherent uniformity, combined with the sensitivity available through quantum effects, makes quantum systems particularly powerful tools for measurements that demand exceptional precision.

Quantum vs Classical Sensing: Core Differences

The central difference between classical and quantum sensing lies in how precisely each can measure changes in the physical world. Classical sensors rely on conventional physical effects, such as the compression of a spring or changes in electrical resistance, to detect and measure environmental changes.¹ Their sensitivity is ultimately constrained by the standard quantum limit, which places a boundary on measurement precision.²

Quantum sensing uses properties such as superposition and entanglement to push beyond that boundary.⁶ In quantum metrology, these resources can reduce measurement uncertainty below the standard quantum limit and move closer to the Heisenberg limit, where measurement precision can improve more rapidly as additional quantum resources are used.² The result is greater sensitivity to extremely small changes that conventional sensing methods may be unable to detect.¹

Real-World Quantum Sensing Applications

Quantum sensing may sound like technology for the distant future, but some of its applications are already well established. Atomic clocks provide the extraordinarily precise timing that supports GPS, while magnetic resonance imaging relies on quantum properties to produce detailed images of structures inside the human body.³

Greater sensitivity and precision could make quantum sensing useful in applications that conventional sensors cannot support as effectively.³ Emerging uses could include detecting underground mineral deposits, monitoring infrastructure, studying materials, and developing navigation systems that do not depend on GPS.^{1, 3}

Healthcare and Quantum Magnetometry

Quantum magnetometry uses quantum systems to measure extremely weak magnetic fields. In healthcare, that sensitivity could expand what researchers and clinicians can learn from the magnetic fields produced by activity in the human brain. Optically pumped magnetometers, for example, are being developed for magnetoencephalography (MEG), which measures magnetic fields generated by brain activity.⁷ Unlike conventional MEG sensors that require cryogenic cooling, these sensors can operate without cryogenics and be positioned closer to a patient’s scalp.⁷

That closer proximity can increase the strength of the measured magnetic fields, improving sensitivity and spatial resolution.⁷ Studies of optically pumped magnetometers have also demonstrated stronger response amplitudes while capturing brain dynamics comparably to conventional MEG systems.⁸ Together, these capabilities could give researchers and clinicians a more precise, noninvasive way to study how the brain functions.^{7, 8}

Astrophysical and LIGO Gravitational Waves

At an entirely different scale, quantum sensing is helping scientists detect distant cosmic events. Those events can produce gravitational waves that cause extraordinarily small distortions in spacetime by the time they reach Earth. The Laser Interferometer Gravitational-Wave Observatory (LIGO), which operates detectors in Washington and Louisiana, detects those waves by measuring minute changes in the length of its four-kilometer detector arms.⁴

Scientists use squeezed light to reduce quantum noise that would otherwise limit the precision of those measurements.⁴ As part of the LIGO A+ upgrade, researchers added a 300-meter-long vacuum filter cavity at each detector to enable frequency-dependent squeezing across a broader range of frequencies.⁹ The resulting reduction in quantum noise increased LIGO’s detector range by almost 20%, giving scientists greater ability to detect gravitational-wave events from farther away.⁹

Put Quantum Innovation Within Reach

Quantum sensing demonstrates what becomes possible when engineers learn to work with the fundamental properties of matter rather than around their limitations. From measuring brain activity to detecting gravitational waves, advances in sensing are expanding the boundaries of what scientists and engineers can observe, measure, and understand.

UC Santa Barbara’s 100% online Master of Engineering and Technology Leadership (METL) program can help you develop the technical depth and leadership skills to contribute to advances in quantum technology. The Quantum Information track combines specialized technical coursework taught by UCSB engineering faculty and industry experts with business, leadership, and technology management courses. As you deepen your understanding of quantum technologies, you’ll strengthen the communication, decision-making, and strategic leadership skills you need to guide complex technical work.

Designed for working professionals, METL offers flexible pacing that allows you to continue building your career while earning your degree. Explore the program’s admission requirements and curriculum, start your application, or contact us to discuss how METL can support your professional goals.

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