Physicists Design a Way to Detect Quantum Behavior in Large Objects, Like Us (sciencealert.com) 20
Researchers have developed a way to apply quantum measurement to something no matter its mass or energy. "Our proposed experiment can test if an object is classical or quantum by seeing if an act of observation can lead to a change in its motion," says physicist Debarshi Das from UCL. ScienceAlert reports: Quantum physics describes a Universe where objects aren't defined by a single measurement, but as a range of possibilities. An electron can be spinning up and down, or have a high chance of existing in some areas more than others, for example. In theory, this isn't limited to tiny things. Your own body can in effect be described as having a very high probability of sitting in that chair and a very (very!) low probability of being on the Moon. There is just one fundamental truth to remember -- you touch it, you've bought it. Observing an object's quantum state, whether an electron, or a person sitting in a chair, requires interactions with a measuring system, forcing it to have a single measurement. There are ways to catch objects with their quantum pants still down, but they require keeping the object in a ground state -- super-cold, super-still, completely cut off from its environment. That's tricky to do with individual particles, and it gets a lot more challenging as the size of the scale goes up.
The new proposal uses an entirely novel approach, one that uses a combination of assertions known as Leggett-Garg Inequalities and No-Signaling in Time conditions. In effect, these two concepts describe a familiar Universe, where a person on a chair is sitting there even if the room is dark and you can't see them. Switching on the light won't suddenly reveal they're actually under the bed. Should an experiment find evidence that somehow conflicts with these assertions, we just might be catching a glimpse of quantum fuzziness on a larger scale.
The team proposes that objects can be observed as they oscillate on a pendulum, like a ball at the end of a piece of string. Light would then be flashed at the two halves of the experimental setup at different times -- counting as the observation -- and the results of the second flash would indicate if quantum behavior was happening, because the first flash would affect whatever was moving. We're still talking about a complex setup that would require some sophisticated equipment, and conditions akin to a ground state -- but through the use of motion and two measurements (light flashes), some of the restrictions on mass are removed. [...] "The next step is to try this proposed setup in an actual experiment," concludes the reports. "The mirrors at the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the US have already been proposed as suitable candidates for examination."
"Those mirrors act as a single 10-kilogram (22-pound) object, quite a step up from the typical size of objects analyzed for quantum effects -- anything up to about a quintillionth of a gram."
The findings have been published in the journal Physical Review Letters.
The new proposal uses an entirely novel approach, one that uses a combination of assertions known as Leggett-Garg Inequalities and No-Signaling in Time conditions. In effect, these two concepts describe a familiar Universe, where a person on a chair is sitting there even if the room is dark and you can't see them. Switching on the light won't suddenly reveal they're actually under the bed. Should an experiment find evidence that somehow conflicts with these assertions, we just might be catching a glimpse of quantum fuzziness on a larger scale.
The team proposes that objects can be observed as they oscillate on a pendulum, like a ball at the end of a piece of string. Light would then be flashed at the two halves of the experimental setup at different times -- counting as the observation -- and the results of the second flash would indicate if quantum behavior was happening, because the first flash would affect whatever was moving. We're still talking about a complex setup that would require some sophisticated equipment, and conditions akin to a ground state -- but through the use of motion and two measurements (light flashes), some of the restrictions on mass are removed. [...] "The next step is to try this proposed setup in an actual experiment," concludes the reports. "The mirrors at the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the US have already been proposed as suitable candidates for examination."
"Those mirrors act as a single 10-kilogram (22-pound) object, quite a step up from the typical size of objects analyzed for quantum effects -- anything up to about a quintillionth of a gram."
The findings have been published in the journal Physical Review Letters.
Re: (Score:2)
i dont get it (Score:4, Funny)
given the effort it takes to keep 40 qubits isolated, how hasnt every single particle in someones body not had its waveform collapsed? like, arent most waveforms collapsed apart from intergalatic rays yet to bounce into anything?
Re: (Score:2)
Well they did say a dark room, not a room where you and everything in the room is glowing in infrared.
Re: (Score:2)
but the waveforms have already collapsed, regardless of whether you turned the light off havent they? and dont radio waves similarly break the quantum state, or any other type of subatomic particle?
Re: (Score:2)
Re: (Score:2)
Re: (Score:2)
It is often poorly presented to the public. Like if the "knowledge" of a quantum object collapsed it by some miracle of philosophy.
To observe an object (quantum or not) you must touch it. For example to "see" an object , someone must have sent at least a photon to that object and that object has re-emitted this photon towards your eye. Same reasoning with any interaction. Magnetic, gravitation. You touch and modify what you observe.
Re: (Score:2)
Re: (Score:2)
just like an the moon disappears if everyone on earth looks away
Try this at home (Score:5, Interesting)
If someone is looking at me, how is that going to change what I am doing? It won't.
The problems is that the famous wave we hear about is a wave of probability, and that things we normally view as dimensionally fixed are actually waves.
Position is a wave. As a wave, it can be broken up into 2 component waves sin() and cos(), and both components can be sent on different paths, and this can be done experimentally by hobbyists.
Firstly you need a source of single photons. Take a laser and put it through a filter (originally this was glass held over a candle to make it dark) and measure the light output, and use this to calibrate your filter. One glass reduces the light by a factor of 10, another by a factor of 8.5, and so on.
Take the energy of your laser and add a bunch of the glass plates so that the calculated output energy will be about 1 photon per second. The wavelength determines the photon energy, and the photons collectively make up the total output energy.
Put the output into a photomultiplier and hear it go "click", randomly, about once every second. Add or remove plates as needed. Photomultipliers are available on eBay, and you'll need a power supply, which is easy to build.
Now get 2 mirrors and 2 beam splitters. (You can get these on eBay or Edmund Scientific, or sometimes places like American Science Surplus. Also, you can salvage front surface mirrors and beam splitters from a junked video projector.) Set these up as the traditional split beam experiment [aps.org].
As an aid to visualization, we can imagine the photon going slowly and carrying a lit LED.
The photon leaves the laser, and we see a continuous light from its LED. It gets split at the first beamsplitter - the sin() component goes NORTH, and the cos() component goes EAST. We see the LED first on the N path, then it dies down and simultaneously brightens in the E path, then that dies down and it brightens up on the N path a little further than last time... back and forth until each photon hits the mirrors, then the lower photon goes N while the upper photon goes E, to be combined at the upper beam splitter and then the LED is lit solid coming out the EAST path to the EAST detector.
The EAST detector sees all the photons, none arrive at the NORTH detector.
Put any sensor that observes the photon in either one of the paths. If the sensor is inserted at the point where the LED is lit, the sensor catches the photon and registers the event. The photon stops there, so doesn't continue along the paths.
If the sensor is inserted at the point where the LED is *not* lit, the other side goes full ON and continues down that path. Your sensor did *not* detect the photon, but your observation determined where the photon actually was without observing it. The fully lit LED goes to the 2nd beam splitter and once again gets split into sin() and cos() components, and now the photon will arrive at one or the other detector, randomly.
Not having a sensor makes the photon arrive at the E detector exclusively. Having a sensor either captures the photon, or causes the photon to randomly arrive at the E or N sensor.
This behaviour is almost ineffably weird, it's had physicists scratching their heads for over a century. Lots and lots of experiments plumbing the boundaries of this, noting that you can take a picture of medusa without capturing any photons reflecting from her face, and detect whether a light sensitive bomb would go off without sending it any light.
Measuring the photon where it isn't causes the waveform to collapse and reform as a combined sin() and cos(), in the manner it had when it left the laser.
And then the question arises, what constitutes a measurement that causes this behaviour?
If your method of measure or observation is changing the target, then your method is just bad.
It's an easy experiment to reproduce. Give it a try.
Re: (Score:2)
1st April is still 3 months away (Score:3)
Isn't Quantum behaviour because of the extremely small sizes we are dealing with - where the act of measuring with much larger contraptions disturbs the quantum particles? So, what's the point of trying to observer Quantum behaviour of people or other large objects?
Re: (Score:2)
Does it involve a cat and a box? (Score:2)
Re: (Score:2)
I want to see the interference pattern (Score:4, Funny)