100 Years of Quantum Mechanics: How Schrödinger's Cat Led to Modern Technology

Quantum mechanics, the theory that describes the behaviour of the smallest particles, is about 100 years old.

When it first appeared, many scientists thought it was too strange: the laws of the microcosm didn't fit into conventional logic. But today, quantum physics is at the heart of the technologies we use every day - from lasers and microchips to advanced quantum computers and ultra-secure communications.

A new review in Science by physicist Marlan Scully (Texas A&M University; also affiliated with Princeton University) reminds us of this. In the article, he traces the journey of quantum mechanics from early debates and "thought experiments" to practical applications that are changing science and industry.

How it all began: Schrödinger's cat and the oddities of the microcosm

One of the most famous symbols of quantum 'weirdness' is the 'Schrödinger's cat' paradox, proposed in 1935. It was meant to show how unfamiliarly quantum theory describes the state of a system before measurement. These days, such ideas are no longer just philosophy: they are the basis for the development of quantum computing and quantum cryptography, areas where effects like superposition and entanglement are important.

The key idea that changed the technique: coherence

One of the key "quantum tools" is coherence: when particles (e.g. atoms and photons) act in concert as a single system. This was the foundation for lasers - once thought almost impossible, lasers are now everywhere: barcode scanners, medicine (including eye surgery), industry and research.

Coherence is also closely related to quantum entanglement, a phenomenon that Einstein called "spooky action at a distance." Entanglement helps create methods to protect data in quantum communications and increase the sensitivity of ultra-precise devices.

"Quantum engines" and attempts to rewrite classical limits

Scully also speculates about quantum heat machines: in classical physics, engine efficiency is limited by the "Carnot limit", but quantum effects can change familiar limits and suggest new approaches to energy management - although this is still an area of active research.

From biology to space

Quantum methods are increasingly being applied outside of "pure physics" as well. For example, spectroscopic techniques make it possible to study molecules and viruses on very small scales. And at the level of the Universe, the big goal remains - to combine quantum mechanics with relativity (quantum gravity, attempts to explain black holes and the early Universe).

Another unexpected area is turbulence (chaotic vortices in air and water), on which weather, climate and flight safety depend. Studies of quantum fluids, such as superfluid helium, are helping to look for patterns that may also be useful for "ordinary" flows.

What's next

Despite a century of successes, quantum mechanics still has big questions: whether gravity can be "quantised", how quantum computers will affect medicine and materials, and what new effects quantum technology will unlock.

5 ways quantum mechanics "works" in our lives

1. Lasers - from checkout scanners to surgery.
2. Secure communications - quantum cryptography for data transmission.
3. Fast computing - quantum computers for tasks that are too complex for conventional ones.
4. Ultra-precise measurements - including technologies that increase the sensitivity of gravitational wave detectors.
5. Medicine and biology - methods for imaging and analysing molecules at the nanoscale.