Ask any question you want about Physics

a reply to: pfishy
You didn't ask the only question that really matters to most people:

Is the D-wave really significantly faster than classical computers?

This article in nature addresses that most significant question and also answers your question about whether it really uses quantum phenomena:

D-Wave upgrade: How scientists are using the world’s most controversial quantum computer

24 January 2017
...
D-wave’s qubits are much easier to build than the equivalent in more traditional quantum computers, but their quantum states are also more fragile, and their manipulation less precise. So although scientists now agree that D-wave devices do use quantum phenomena in their calculations, some doubt that they can ever be used to solve real-world problems exponentially faster than classical computers — however many qubits are clubbed together, and whatever their configuration.
...
D-wave machines are a long way from showing the exponential speed increase over classical computers that their advocates hope to see. But in a paper posted on 17 January and not yet peer-reviewed, a D-Wave team claimed the 2000Q could find solutions up to 2,600 times faster than any known classical algorithm...Now the onus will be on sceptics to try to find a faster classical algorithm. “All I know is that, in the now two or three previous cases where we were in this same situation, it did turn out that a different classical solver eliminated the claimed gap,” says Scott Aaronson, a computer scientist at the University of Texas at Austin.

Maybe they will find a niche somewhere but obviously computer scientists like Scott Aaronson are skeptical based on finding classical solutions to close previously claimed gaps.

Even Scott Aaronson admits D-Wave's 15 million dollar chip is faster than the class of processor you'd find in your laptop, a marketing strategy used by D-wave to create impressive but misleading claims.

Biggest ever quantum chip announced, but scientists aren't buying it

Scott Aaronson of the University of Texas and Greg Kuperberg of UC Davis tell The Verge that while there was theoretical hope that quantum annealing would produce results, the tests have not borne this theory out. The pair note that papers published by D-Wave and partners supposedly showing its quantum advantage are generally pitting its $15 million chips against the class of processor you’d find in your laptop. What’s more, they say, testers tend to pick computational challenges optimized for D-Wave's chips, giving the company’s tech a home-field advantage. This, they say, leads to impressive but misleading claims that D-Wave's technology has been proved to be "100,000,000 times faster" than classical computers.

So maybe if you pit a 15 million dollar Dwave processor against the processor in your laptop it looks pretty good, but in a more fair test against more appropriate classical competition, not so much.

a reply to: Arbitrageur

I'd heard the results were cherry picked with the 9 qbit machine. Custom algorithms and such. But the 49 qbit machine seems like it would be the line in the sand for proof of concept, given the previous seeming fakery.
But I'm actually interested in the components of the qbit system and it's peripheral connections. What are the actual qbits constructed from, and how does the i/o system input and interpret data to and from these qbits.
If you'd rather, I can just try to find the specifics myself (again). I just haven't been very successful searching for it so far, so I was hoping someone here might know.

a reply to: pfishy
Download the pdf linked here, which should answer many questions about how the Dwave computer qubits work:

Entanglement in a Quantum Annealing Processor

What some people are saying is that the Dwave qubits are so fragile etc that it doesn't matter how much they scale it. Only time will tell who is right.

Can the future affect the past?

a reply to: Arbitrageur

Thanks once again! I'll be back next time I'm feeling science stupid.

originally posted by: Aytakan
Can the future affect the past?

A layperson's "classical" view of the delayed choice quantum eraser experiment might suggest that, and some find the results "shocking".

To the physicist, the results "are all consistent with prediction." To the layperson, the results should be shocking.

However physicists have been confirming for the last century that the classical view is not how nature really works, and they have come up with interpretations such as the "Copenhagen Interpretation" to explain to their students how to predict experimental results. If the delayed choice quantum eraser experiment is viewed through the physicist's "Copenhagen interpretation", there is no time paradox because the wavefunction is a superposition of states which doesn't behave classically.

There are also alternative interpretations of quantum mechanics besides the Copenhagen interpretation, which are similarly non-classical but explain observations differently (as discussed in the opening post). We don't know which interpretation is correct, but Copenhagen is the one we teach.

a reply to: Arbitrageur

I have read a less detailed article about this experiment somewhat recently. That piece left me with some unanswered questions, but I got wrapped up in something else and forgot to look those answers up.
Thanks for posting this link. I have now quite happily answered those questions from this paper.
That a future interaction could influence events which have already been measured when the second event occurs is extremely counterintuitive for an observer so heavily biased towards the classical realm. But I have read before that quantum events occurring in a forward or backward time direction are virtually indistinguishable from one another.

a reply to: Arbitrageur

Given that is it possible that future placement of celestial bodies is the dark energy that is pulling apart the universe?

Its future gravitational pull? I recall gravity being able to transcend time. Hell even the fact the universe exists now is the reason it exists in the first place?

a reply to: Aytakan
Dark energy is thought to be vacuum energy. We don't fully understand it but it doesn't seem necessary to invoke any time paradoxes to explain it, we think it's just a property of empty space which we know to not be really "empty".

Also gravity tends to pull things together, so it can't explain dark energy which is doing the opposite.

Gravity doesn't "transcend time". It's difficult to get as precise a measurement on the speed of gravity as with the speed of light which can be measured very precisely, but the rough measurements made so far of the speed of gravity suggest it may travel at the speed of light as theorized, so as long as the speed of light (and the speed of gravity if the same) limits causality, we don't have time paradoxes.

One thing that does appear to travel faster than light is the correlation between entangled particles but this happens in such a way as to not result in any causality violations, so far as we have determined in experiments to date. It's an interesting area of research because we would have to re-think our models if it did result in causality violations.

a reply to: Arbitrageur

Thanks for the clear explanation.
Great job.

Apologize for a bad english.
I've been into deep science for about 14 years, although I wish you consider me as not a Scientist.

I appreciate if you have something to share about the current science dilemma. This doesn't include any current theories of we all mostly know of. And no, it's not metaphysics. If you are aware of what I mean, can you point the current's mind-bloggling subject that remain in the very edge of a eternal paradox? Please not multiverses and parallel existences within space-time and so on. Also:

1. If the simple fact that between 0 and 1, there is infinite, how deep would you want to find answers?
2. Considering that - of course - we don't know anything - could you elaborate how would you dream upon the final (or most satisfying) truth of all?

originally posted by: zundier
I appreciate if you have something to share about the current science dilemma....... If you are aware of what I mean, can you point the current's mind-bloggling subject that remain in the very edge of a eternal paradox?

Might need to clear that up for us... what current science dilemma? Im a professional scientist and have no clue what you are talking about.

1. If the simple fact that between 0 and 1, there is infinite, how deep would you want to find answers?
2. Considering that - of course - we don't know anything - could you elaborate how would you dream upon the final (or most satisfying) truth of all?

1.... that is not fact simple or otherwise, it is a somewhat ambiguous and partially meaningless question
2.... Again, it is not true that we dont know anything... we do know or at least understand some... things... So once more the question is ambiguous

Maybe have to reword things in a less pretentious manner?

Regarding physics, from Cosmic Expansion to superclusters to singularities, down to atoms, nuclei, quarks, leptons, neutrinos and all the way down to the Planck Volume and Quantum Foam, do you think we have passed the halfway point in our knowledge of how these function and interact?
To put it another way, from Cosmic to Quantum, do you think there is more we know than don't know regarding the structure and function of the physical universe?

Might need to clear that up for us... what current science dilemma? Im a professional scientist and have no clue what you are talking about.

Have you ever measured the Speed of Light? If so, did you measure again?

1.... that is not fact simple or otherwise, it is a somewhat ambiguous and partially meaningless question

What do you mean by ambiguous? If science is based on Math, and between 0 and 1 there's literally infinite possibilities, please elaborate?

2.... Again, it is not true that we dont know anything... we do know or at least understand some... things... So once more the question is ambiguous

Forgive me for bad english. Of course we're certain about lot's of things in life. I'm just curious of your opinion as a professional scientist regarding the possibility of an ultimate truth? Surely we're are Zillions from it, from Science. But is it achievable? If Yes, is it based on Mathematics? If so, would you please count from 0 to 1?


Just like to add: I'm no one, not scientist, not even close. Just curious and love science. I don't mean to be aggressive, sorry if english writing may look like it.

a reply to: zundier

Well, you can always add another decimal place behind the 0, so the possibilities to subdivide 1 would be infinite, I suppose.
But, for infinite possibilities, I prefer pi. As it is a non-repeating and as far as we know endless string of decimal places, it's wholly possible that every answer to every equation, and every conceivable bit of knowledge, is encoded within that value.
Of course, that's a bit of uninformed numerical mysticism on my part, but I've never come across any evidence to the contrary.

a reply to: pfishy

First question about the Speed of Light was ignored.

From what I've researched, Speed of Light was never measured and resulted on the same value. Not once.

Surely it's always very close and guide us to proper understanding of everything else. Always with flaws from all uncertain measurements.

I wonder, could be possible to blasphemy and say that even Mathematics could have fluctuations and - although perfect - it's never exact?

a reply to: zundier

Your questions were directed to ErosA433. I was simply contributing my thought on one of them
I'm not a scientist, either, and do not have the means to measure the speed of light even if I wanted to do so.

originally posted by: zundier
Apologize for a bad english.
...If you are aware of what I mean....

If you have a question to ask please ask it. I find this game of "try to guess my question" quite annoying and unnecessary. I'm not aware of what you mean, and I don't care to guess when you could simply state your question.

1. If the simple fact that between 0 and 1, there is infinite, how deep would you want to find answers?

I think Eros was too generous in saying that is a "somewhat ambiguous and partially meaningless question". 0 and 1 without any further context are abstractions with no meaning in the real world. For a mathematician, no meaning in the real world is required for mathematical abstractions, but for a physicist, mathematics is a tool to try to describe and predict how nature works in the real world. This means at some point the 0 and the 1 or more commonly variables are correlated with observables or other parameters in the real world.

If you try to correlate those numbers with real world concepts, it's not necessarily true that there's an infinity between them though that's possible. Take for example the density of water which under specified conditions of temperature and pressure is 1.0 g/cc. If you could remove every water molecule from that cubic centimeter you'd have a density of 0 g/cc. But between density of 0 and density of 1 of a cubic centimeter, there are a finite number of molecules, it's not infinite, so your abstraction doesn't seem to hold true in this example. (I think there's something like 33415113400 trillion molecules of water in a cubic centimeter at 1.0 density, so it's a big number and hard to count, but definitely not infinite).

2. Considering that - of course - we don't know anything - could you elaborate how would you dream upon the final (or most satisfying) truth of all?

We do know some things and are grossly ignorant of others. As Eros said it's inaccurate to say we don't know anything. I think the most brilliant statement I've heard about uncovering truth was made by Richard Feynman:

"The way I think about what we're doing is we're exploring, we're trying to find out as much as we can about the world. People say to me 'Are you looking for the ultimate the laws of physics?'. No, I'm not. I'm just looking to find out more about the world. And if it turns out there is a simple ultimate law that explains everything, so be it, that would be very nice to discover. If it turns out it's like an onion with millions of layers and we just sick and tired of looking at the layers, then that's the way it is. But whatever way it comes out, it's nature, it's there and she's gonna come out the way she is. And therefore when we go to investigate it we shouldn't pre-decide what it is we're trying to do except to find out more about it. The problem is why do you find out more about it? If you thought that you were trying to find out more about it because you're going to get an answer to some deep philosophical question you may be wrong. It may be that you can't get an answer to that particular question by finding out more about the character of nature. But I don't look at it - my interest in science is to simply find out about the world. And the more I find out the better it is. I like to find out."

originally posted by: pfishy
Regarding physics, from Cosmic Expansion to superclusters to singularities, down to atoms, nuclei, quarks, leptons, neutrinos and all the way down to the Planck Volume and Quantum Foam, do you think we have passed the halfway point in our knowledge of how these function and interact?
To put it another way, from Cosmic to Quantum, do you think there is more we know than don't know regarding the structure and function of the physical universe?

It's difficult to say how far your journey has progressed when you don't know the location of the destination, if there even is such thing as a destination in the discoveries of science...it could be a never-ending journey.

Do cars get poorer gas milage on particularly hot days?

a reply to: BASSPLYR
It depends. If the car is equipped with air conditioning and it's run a lot on those hot days, then yes running the A/C has an adverse effect on fuel economy.

If there's no A/C or if it's broken or isn't run, then you might actually get better gas mileage in warmer weather, but this is because summer gasoline is re-formulated to a lower vapor pressure, higher fuel economy mixture in the warm weather months. The on average longer molecular chains contain more energy thus result in better fuel economy compared to the shorter molecular length winter formulas, which are easier to turn to vapor but contain less energy. Offsetting this is slightly increased drag if your windows are rolled down but this is more noticeable at higher (highway) speeds than at lower speeds in say residential areas.

More about how physics affects your fuel economy here:

Five properties of physics that affect your gas mileage