Back to Basics, Double Slit Experiment...

[FreakBoy]

I'm delurking for some help with some basic quantum curiosity.

I'm fairly comfortable with the double slit experiment. What I would like to know is what would happen with a slight modification.

If instead of using single particles or a bunch.... what if everything ejected at it was an entangled pair of particles. Would the two entangled particles modify the interference pattern in any way?

I recall reading of experiments where entanglement was used for other measures, but I haven't read of any where both of the entangled particles were aimed at the same double slit.

 

[Vim Razz]

There's a basic problem with trying to use entangled particles for the double slit experiment: The entagled particles tend to shoot off in opposite directions from one another and loose their entaglement as soon as they bounce off something else. ("bounce", of course, is being used here as a shorthand for any strong interaction -- i.e. absorption/re-emmition, etc.)

If you could somehow find a way to direct a pair of entangled particles in the same direction, though, it'd be a pretty awesome experiment.

 

[FreakBoy]

By strong interaction wold we have to rule out using something like th LHC?

 

[Vim Razz]

I have no clue.

It's an interesting idea, but my knowlege of QM isn't quite sophisticated enough to make any educated guesses either way as to what would be required or how it might turn out.

 

[nathan]

How are they entangled? You need to be more specific.

Let's take a simple case: two entangled photons such that they have opposite spins. They'll also have the same wavelength (otherwise they'd be distinguishable).

The diffraction pattern is a property of wavelength, not spin. I don't see why having entangled photons would make a difference.

Did you have a different case in mind?

 

[FreakBoy]

How are they entangled? You need to be more specific.

Let's take a simple case: two entangled photons such that they have opposite spins. They'll also have the same wavelength (otherwise they'd be distinguishable).
The diffraction pattern is a property of wavelength, not spin. I don't see why having entangled photons would make a difference.

Did you have a different case in mind?

You have pretty much answered my question... Entanglement wouldn't affect the experiment in any way.

Well what if they were entangled electrons with opposite charge?

 

[ben m]

You have pretty much answered my question... Entanglement wouldn't affect the experiment in any way.

Well what if they were entangled electrons with opposite charge?

Entanglement is not a generic property---you can't just say "These two particles were entangled, what happens next?" You need to specify what entangled state the pair is in, then we can tell you how that state will behave.

 

[FreakBoy]

Entanglement is not a generic property---you can't just say "These two particles were entangled, what happens next?" You need to specify what entangled state the pair is in, then we can tell you how that state will behave.

Looks like I have more reading to do!



Tangent: Is it bad that reading about quantum mechanics gets me so excited that it keeps me up at night?

 

[The Man]

Looks like I have more reading to do!



Tangent: Is it bad that reading about quantum mechanics gets me so excited that it keeps me up at night?

Not as long as you do not have to get up for anything important in the morning.

You have pretty much answered my question... Entanglement wouldn't affect the experiment in any way.

Well what if they were entangled electrons with opposite charge?

An “electron” with opposite charge is a Positron.

 

[dropzone]

My wife claims to be related to Robert Millikan, who discovered the charge of the electron. We watched a program that had a dramatization in which he crossed out any value outside of what he had predicted.

Me: "No fair! He fudged his data!"

Wife: "You get a Nobel for knowing WHAT data to fudge. He recognized WHY those points were off--experimental error, mostly--and kept the good data."

Twenty-five years later I'm still sputtering.

 

[blutoski]

My wife claims to be related to Robert Millikan, who discovered the charge of the electron. We watched a program that had a dramatization in which he crossed out any value outside of what he had predicted.

Me: "No fair! He fudged his data!"

Wife: "You get a Nobel for knowing WHAT data to fudge. He recognized WHY those points were off--experimental error, mostly--and kept the good data."

Twenty-five years later I'm still sputtering.

Interesting example. Two things that are true:

• Millikan's results were a little off, although close. Keeping some of those discarded values might have made his original value for the electron charge more accurate. The interesting history is that graduate students repeating his experiment reported values that were slightly different each time. Over the years, e gravitated to what we use today.
• We still routinely discard 'outliers'. We have a more established and widely accepted threshold for determining what is an outlier, today. Discarding outliers is not considered 'fudging data'.