Tibbles Is Not a Detector: The Sceptic’s Guide to Quantum Cat Flaps

British homes contain two things in abundance: draughts and opinions about the cat. The cat flap sits at the intersection of both. It is a humble rectangle of plastic, often installed at a slight angle by someone who claimed to have read the instructions, and it has now become the latest unlikely staging ground for quantum hype. As of 2026, the pet-tech aisle is full of flaps that claim to recognise your cat, log her comings and goings, and occasionally imply that they know what she is thinking. Somewhere in the marketing copy, the word ‘quantum’ has started to appear like a cat that has found a warm laptop.

So let us be clear from the start: your cat is not a measurement device. She is a warm, damp, opinionated decoherence machine with a talent for sitting on the exact piece of paperwork you need. The cat flap is not an observer in the quantum sense. And ‘observed’ does not mean ‘watched by a cat’—no matter how judgemental she looks through the glass.

The thought experiment that got out

Schrödinger’s cat was never a proposal for feline quantum computing. In 1935, Erwin Schrödinger used a cat in a box to point out how absurd it sounded to apply quantum rules—superposition, collapse, all that—to everyday objects. The cat was a rhetorical device, not a laboratory animal. He was not saying that Tibbles is simultaneously asleep and demanding breakfast. He was saying that if your theory implies that, your theory has a public relations problem.

The modern version of the confusion is subtler. People hear ‘observation’ and picture a conscious watcher: a scientist, a camera, or a cat with a flicking tail. In quantum physics, measurement is not about eyeballs. It is about physical interaction and the leaking of information into the environment. A detector is anything that leaves a stable record: a click, a pixel, a latch, a memory bit. A cat flap can leave a record—‘something went through at 03:14’—but that does not make it a quantum measuring device. It makes it a plastic door with a sensor.

What measurement actually does

I asked Dr Priya Raman, a quantum physicist who has spent more time than is healthy explaining superposition to people holding mugs, how she would put it. ‘Measurement is not a glance,’ she said. ‘It is a physical correlation. If a system interacts with an environment in a way that leaves a record, the delicate phase relationship between different possibilities leaks away. That is decoherence. It is not mystic. It is what happens when the universe starts keeping notes.’

This is why the cat is irrelevant in the quantum sense. A cat is large, warm, wet, noisy and thoroughly entangled with the air around her. If you put a fragile quantum system in a box with a cat, the box is the problem. The cat will decohere the contents simply by being a cat: breathing, radiating heat, jiggling, shedding. She does not need to look at anything. Her fur is already a record of where she has been.

The engineer’s view: a latch, not an oracle

Malcolm Evans has fitted more cat flaps than he cares to remember, mostly in the sort of British back doors where the draught arrives before the visitor. He is admirably unsentimental about the technology. ‘A microchip flap is a radio reader and a latch,’ he told me. ‘It knows whether the tag is within a few centimetres. It does not know where the cat is. It certainly does not know where the cat is going to be. If it did, I would be charging more.’

That is the useful distinction. A standard microchip flap answers a classical question: is the correct tag nearby? A smart flap might add a schedule, an app, a notification, maybe a small camera. All of that is ordinary sensing and ordinary software. It can be genuinely useful—especially if you have a cat that treats the neighbourhood like a personal buffet—but none of it requires a qubit. A flap that learns your cat’s routine is a spreadsheet with whiskers. A flap that claims to know where Tibbles is before she does is making a prediction based on past behaviour, not performing a quantum measurement.

Decoherence is not a draught

This is where the cat-flap metaphor earns its keep. A draught is moving air. It pushes the flap, rattles the hinge and makes the kitchen feel like a bus shelter. Decoherence is not a draught. It is information leaking into the environment. In a quantum experiment, the enemy is not a cold breeze; it is any interaction that allows the environment to learn which path the system took. Once that information exists somewhere—in a photon, a phonon, a stray molecule—the interference is gone.

A cat flap in a British home has both problems. It has a draught, and it has an environment. The draught is classical and annoying. The environment is classical and also annoying, but in a way that matters for quantum hardware. You cannot fix decoherence by putting a brush strip around the edge. You need isolation, shielding, cooling and a great deal of patience. You do not need to ask the cat to stop observing.

The smart-flap sales pitch

As of 2026, the pet-door market is full of clever language. Flaps learn. Flaps predict. Flaps send notifications. Somewhere in the copy, ‘quantum’ may appear as a decorative adjective, like ‘artisan’ on a bag of crisps. The sceptical questions are the same ones you would ask of any quantum claim. What is the qubit? Where is it isolated? What record does the measurement leave? What advantage does quantum mechanics provide over a microchip and a bit of common sense?

If the answer is ‘none, but it sounds advanced’, you are not looking at quantum technology. You are looking at a cat flap with a marketing department. That is not a crime. It is just not physics.

Let Tibbles be classical

Your cat does not collapse wavefunctions by walking through a door. She collapses cardboard boxes by sitting in them. She does not need to be observed to become real; she is already real enough to wake you at 4am for reasons known only to herself. The cat flap is a useful, slightly draughty piece of British engineering. It is not an observer, an oracle, or a quantum device.

So the next time a smart flap claims to know where Tibbles is before she does, ask it a simple question: is that a quantum measurement, or have you just been reading her calendar? The answer will almost certainly be the latter. And Tibbles, who has been listening from the windowsill, will remain gloriously, classically unimpressed.