August 16, 2016 report

# Physicist claims to have observed quantum effects of Hawking radiation in the lab for the first time

(Phys.org)—Jeff Steinhauer, a physicist at the Israel Institute of Technology, has published a paper in the journal *Nature Physics* describing experiments in which he attempted to create a virtual black hole in the lab in order to prove that Stephen Hawking's theory of radiation emanating from black holes is correct —though his experiments are based on sound, rather than light. In his paper, he claims to have observed the quantum effects of Hawking radiation in his lab as part of a virtual black hole—which, if proven to be true, will be the first time it has ever been achieved.

For many years, scientists believed that nothing could ever escape from a black hole. But in 1974, Stephen Hawking published a paper suggesting that something could—particles that are now called Hawking radiation. His idea was that if a particle (and its antimatter mate) appeared spontaneously at the edge of a black hole, one of the pair might be pulled into the black hole while the other escaped, taking some of the energy from the black hole with it—which would explain why black holes grow smaller and eventually disappear. Because such emissions are so feeble, no one has been able to measure Hawking radiation, so researchers have instead tried to build virtual black holes in labs to test the theory. One type of virtual black hole was proposed back in 1981 by Bill Unruh with the University of British Columbia—he suggested that an analogue might be created using water instead of light. He imagined a phonon existing at the edge of a waterfall—as the water speeds up, it begins to move faster than the speed of sound, causing it to be trapped. But if the phonon had an entangled mate that eluded the fall by moving away before getting caught up, it could escape. In this new effort, Steinhauer has built a device based on that idea and in so doing, claims he has observed an analogue of Hawking radiation.

The experiment consisted of creating an entangled pair of phonons sitting inside a bit of liquid that had been forced (via laser) to move very fast and then observing the action as one of the pair was pulled away as the liquid began to move faster than the speed of sound, while the other escaped—the fluid was a Bose-Enistein condensate of rubidium-87 atoms. After repeating the experiment 4,600 times Steinhauer became convinced that the particles were entangled, a necessity for a Hawking radiation analogue. His findings do not prove Hawking's theory to be true, of course, but they do appear to add a degree of credence that other researchers have thus far not been able to achieve.

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**More information:**Jeff Steinhauer. Observation of quantum Hawking radiation and its entanglement in an analogue black hole,

*Nature Physics*(2016). DOI: 10.1038/nphys3863

**Abstract**

We observe spontaneous Hawking radiation, stimulated by quantum vacuum fluctuations, emanating from an analogue black hole in an atomic Bose–Einstein condensate. Correlations are observed between the Hawking particles outside the black hole and the partner particles inside. These correlations indicate an approximately thermal distribution of Hawking radiation. We find that the high-energy pairs are entangled, while the low-energy pairs are not, within the reasonable assumption that excitations with different frequencies are not correlated. The entanglement verifies the quantum nature of the Hawking radiation. The results are consistent with a driven oscillation experiment and a numerical simulation.

© 2016 Phys.org

**Citation**: Physicist claims to have observed quantum effects of Hawking radiation in the lab for the first time (2016, August 16) retrieved 22 August 2019 from https://phys.org/news/2016-08-physicist-quantum-effects-hawking-lab.html

## User comments

dirk_bruereBenni......."and eventually disappear", like to where? Back into the Universe? How does matter "disappear" & become non-existent if that is what is meant by "disappear"? There is Einstein's Mass/Energy Equivalence Principle to deal with here, so within the context of the word "disappear" what is that supposed to mean?

RNPYou got it right first time. The Hawking radiation carries the mass/energy of the black hole back out into the universe.

Benni.......and this of course would be Einstein's Mass/Energy Equivalence Principle, but the article by its use of the word "disappear" make it sound like mass is simply obliterated by disappearing into some nether region commonly described as an infinitely dense well of gravity, a situation belying the concept of Conservation of Energy within the context of Special relativity.

RNPtpbWe don't know if Black holes shrink and disappear.

We don't know if hawking radiation exists.

That is Hawkings theory, and is unproven.

RNPYou are right. But experiments like this at least give indirect support to Hawkings' ideas.

BenniAuthor, Jeff Steinhauer: What do you mean by "disappear"?

RealityCheckConsider: If virtual pair is separated/become real particles with real energy content, then both particles will take their respective energy content in their respective directions into/away from the black hole (as hypothesized by Hawking). HOWEVER: If both particles have equal partition of the energy-space involved in their paired creation/separation, then the TOTAL COMBINED energy remains the same; with one HALF going INTO the BH and one HALF going AWAY into the wider Universal energy-space (as hypothesized by Hawking).

Hence a QUESTION which I have long asked (but NOT YET seen tenably answered by proponents of that hypothesis):

My QUESTION to you all now is:

How can a BH be diminished by that hypothesized process which INCREASES the BH energy by an amount of energy content contributed by the IN FALLING particle?

NOTE WELL: 1) No "negative energy" is known to exist; and, 2) All energy, has real gravitic effect.

Cheers all. :)

big_hairy_jimboBenniEnergy contributed by an IN FALLING particle must come about as a result of TRANSFORMATION of the mass of that particle to energy. The Author's point is that the BH radiates ENERGY away (?) from the BH such that incoming energy is less than the energy that "disappears", the BH is starved for Mass/Energy sustenance & consequently the BH just sort of evaporates.

The problem with the Author's theory is that no one has ever seen a BH, so we don't know what to surmise about the stability of existence of such hypothesized stellar bodies, we can't even observe an Event Horizon to know for a fact that such a perimeter of Mass/Energy of NO RETURN even exists.

BenniThis of course brings up matters which conjecture how ENERGY & GRAVITY are related. Both waveforms move at lightspeed, so does this somehow cause them to be intertwined with one another? At the same time we know from Einstein Field Equations that gravity is mass dependent & so is the availability of energy when transformation of mass occurs.

Is it possible there's a transformation process by which ENERGY can be TRANSFORMED to GRAVITY & vice versa is in essence the question you're asking. The fact the two have in common the same velocity leads some to believe in the possibility.

When mass is transformed, the forces of gravity change equivalently between mass & energy. Transforming half of a mass results in half of the gravity leaving the mass & going with the photon output. This is how Einstein knew the speed limitation of gravity was at lightspeed & not instantaneous.

tinitusChiefFartingDogMimath224@tpb, Agree. The other point is, in analogue BH's I would have thought that experimenters know the fate of material after passing through, whereas we still don't know what the real fate of matter is in cosmic BH's.

ColbourneBenniHow would you prove they don't?

If it doesn't there is an Information Loss issue to deal with, & in Einstein's Special Relativity of the Mass/Energy Equivalence Principle Information Loss (Energy) can't happen.

The fact that Einstein's Mass/Energy Equivalence Principle has been "proven" is proof enough that Hawking is on the right track in accounting for Information Loss (Energy) through "hawking radiation". Anyone believing to the contrary must first prove Information Loss can occur before a foundation can be built upon proving Hawking's theory is "unproven".

KronThis is not required. Quantum field theory allows for field excitations, the energy from the black hole is lent out in the creation of the particle antiparticle pair, at annihilation the energy is returned. If the pair is torn apart and one of the particles escapes then the black hole loses the corresponding mass. Empty space is teeming with virtual particle pairs as per perturbation theory of qft. For these particles to become "real" real energy is required (such as gamma rays producing electron positron pairs). In the case of black holes it is the gravitational well that is the black hole that is providing the energy for the pair creation.

This is for you RealityCheck ;)

cheers

BenniYou obviously don't know the difference between Kinetic Energy & Electro-magnetic Energy.

BenniExplain how this makes sense? Explain how ENERGY can move "at less than or equal to lightspeed".

RealityCheckHowever, GR clearly and unambiguously states that the gravitational effect from the BH is only to bias surrounding space, it implies that the energy is already in space, with only the effective direction of its action changed by the BH presence; ie not costing the BH any energy of its own to create its gravitational well.

So if virtual particles separated/made real (ie, persisting quantum fluctuations) by the extreme gradient in near-horizon gravitational well position, then "realized" quantum energy increases Global 'real/persistent' QM field energy while decreasing Global 'virtual/transient' QM field energy....Net ZERO. If 'realised energy' goes into BH its LOCAL real/persistent QM energy increases by that 'half'?

Cheers. :)

BenniIf an explanation can be convoluted & distorted in any way imaginable, you'd be the one to come up with it, then to capstone it, you attribute Special Relativity to zany Zwicky instead of Albert Einstein further demonstrating why you remain mired in 1st semester physics which you probably didn't even pass.

Captain StumpyWTF??

to point out the obvious:

you're the one calling out Jeff Steinhauer to define the word "disappear" so you can understand the above when it was a word that Yirka chose to use in an *article* about Jeff Steinhauer's study

... but you claim that others are making things "convoluted & distorted in any way imaginable"????

GawadThat's because the BH's "LOCALreal/persistent QM energy" as you put it actually initially drops by the equivalent of TWO particles when the pair is created out of the vacuum at the event horizon. Just like the energy level of local space-time "drops" by the equivalent of TWO particles everywhere virtual particle pairs are created (which is everywhere), only normally this goes unnoticed since the mass/energy of the pair balance the energy given up by the local space-time. And then they annihilate and "nothing happened".

It's that the BH only gets back ONE of the TWO particles it put into birthing the PAIR out of its own space-time vacuum. Created inside or outside the BH the pair annihilate normally; only at the horizon and created with momentum perpendicular to the horizon do the special circumstances result in their separation.

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