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How do you know when two objects are so called entangled?


How are atoms entangled, and can it be done remotely?What laser and BBO are needed to create entangled laser streams?How can we know that all of the results for entangled photons are not chosen when the pair is created?how are quantum entangled states mantained?Determining if two qubits in an ensemble are entangledAre particles entangled after beta decay?How can we know if a pair of particles are entangled?Would it be possible to quantum entangle two large objects?Quantum-entangled macroscopic objectsHow do we know that two quantum states are entangled?













10












$begingroup$


I’m not asking how would you entangle two objects. I want to know how would you know they are entangled?










share|cite|improve this question











$endgroup$











  • $begingroup$
    van Enk et al (2007), "Experimental procedures for entanglement verification," Physical Review A 75, 052318 (authors.library.caltech.edu/8289) reviews a few methods, with emphasis on methods that are sufficient if we assume that quantum theory is correct. This is a superset of methods that are sufficient for ruling out local hidden variables.
    $endgroup$
    – Chiral Anomaly
    Mar 29 at 15:45











  • $begingroup$
    @ChiralAnomaly thanks, this Looks like a very thorough article and I will read through it.
    $endgroup$
    – Bill Alsept
    Mar 29 at 18:01















10












$begingroup$


I’m not asking how would you entangle two objects. I want to know how would you know they are entangled?










share|cite|improve this question











$endgroup$











  • $begingroup$
    van Enk et al (2007), "Experimental procedures for entanglement verification," Physical Review A 75, 052318 (authors.library.caltech.edu/8289) reviews a few methods, with emphasis on methods that are sufficient if we assume that quantum theory is correct. This is a superset of methods that are sufficient for ruling out local hidden variables.
    $endgroup$
    – Chiral Anomaly
    Mar 29 at 15:45











  • $begingroup$
    @ChiralAnomaly thanks, this Looks like a very thorough article and I will read through it.
    $endgroup$
    – Bill Alsept
    Mar 29 at 18:01













10












10








10


3



$begingroup$


I’m not asking how would you entangle two objects. I want to know how would you know they are entangled?










share|cite|improve this question











$endgroup$




I’m not asking how would you entangle two objects. I want to know how would you know they are entangled?







quantum-mechanics quantum-entanglement






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Mar 29 at 7:13









Qmechanic

108k122021255




108k122021255










asked Mar 29 at 6:10









Bill AlseptBill Alsept

2,0541723




2,0541723











  • $begingroup$
    van Enk et al (2007), "Experimental procedures for entanglement verification," Physical Review A 75, 052318 (authors.library.caltech.edu/8289) reviews a few methods, with emphasis on methods that are sufficient if we assume that quantum theory is correct. This is a superset of methods that are sufficient for ruling out local hidden variables.
    $endgroup$
    – Chiral Anomaly
    Mar 29 at 15:45











  • $begingroup$
    @ChiralAnomaly thanks, this Looks like a very thorough article and I will read through it.
    $endgroup$
    – Bill Alsept
    Mar 29 at 18:01
















  • $begingroup$
    van Enk et al (2007), "Experimental procedures for entanglement verification," Physical Review A 75, 052318 (authors.library.caltech.edu/8289) reviews a few methods, with emphasis on methods that are sufficient if we assume that quantum theory is correct. This is a superset of methods that are sufficient for ruling out local hidden variables.
    $endgroup$
    – Chiral Anomaly
    Mar 29 at 15:45











  • $begingroup$
    @ChiralAnomaly thanks, this Looks like a very thorough article and I will read through it.
    $endgroup$
    – Bill Alsept
    Mar 29 at 18:01















$begingroup$
van Enk et al (2007), "Experimental procedures for entanglement verification," Physical Review A 75, 052318 (authors.library.caltech.edu/8289) reviews a few methods, with emphasis on methods that are sufficient if we assume that quantum theory is correct. This is a superset of methods that are sufficient for ruling out local hidden variables.
$endgroup$
– Chiral Anomaly
Mar 29 at 15:45





$begingroup$
van Enk et al (2007), "Experimental procedures for entanglement verification," Physical Review A 75, 052318 (authors.library.caltech.edu/8289) reviews a few methods, with emphasis on methods that are sufficient if we assume that quantum theory is correct. This is a superset of methods that are sufficient for ruling out local hidden variables.
$endgroup$
– Chiral Anomaly
Mar 29 at 15:45













$begingroup$
@ChiralAnomaly thanks, this Looks like a very thorough article and I will read through it.
$endgroup$
– Bill Alsept
Mar 29 at 18:01




$begingroup$
@ChiralAnomaly thanks, this Looks like a very thorough article and I will read through it.
$endgroup$
– Bill Alsept
Mar 29 at 18:01










1 Answer
1






active

oldest

votes


















15












$begingroup$

In general you can't. That is, if you have just two particles you cannot tell whether they are entangled or not.



Entanglement reveals itself by correlations. For example if you take many pairs of particles you may find that their properties are always correlated, e.g. their spins are always opposite, and this tells you that whatever mechanism is generating the pairs of particles is entangling them. But this shows up only with repeated measurements. A single measurement cannot tell you the particles are correlated since their spins could have the values you observe just by chance.






share|cite|improve this answer









$endgroup$












  • $begingroup$
    Thanks john, I assumed it involved measuring many pairs. I just wanted to confirm if correlation was the main thing we were looking for. Has anyone ever correlated two large objects which produced measurements of cos2?
    $endgroup$
    – Bill Alsept
    Mar 29 at 7:06











  • $begingroup$
    @BillAlsept That's very technically complicated. Measurement affects the object (as does any other interaction). The bigger the object, the harder it is to isolate from all those influences, and the harder it is to have any confidence in your measurement. There's no reason to expect entanglement "stops" at some scale, but there's many reasons to expect that the bigger the object, the harder it gets to prove entanglement. But we do know it works on a macroscopic scale, because quantum computers are macroscopic (without relying on entanglement of every individual atom involved).
    $endgroup$
    – Luaan
    Mar 29 at 9:21










  • $begingroup$
    @BillAlsept as far as I know this expt is the largest objects ever entangled
    $endgroup$
    – John Rennie
    Mar 29 at 12:07










  • $begingroup$
    @JohnRennie The article is very interesting but it says the two objects are coupled to a circuit and that the circuit keeps the two objects so called entangled. Isn’t that still just a local process? This is probably more of a question for chat But the only correlations I can think of are mirrored variables from a common source. Which is not really entanglement and why I say so called entanglement. I guess what I’m saying is I could draw up an experiment where many pairs of large objects are correlated with given variables that when tested would give the results of cos2. Thanks
    $endgroup$
    – Bill Alsept
    Mar 29 at 15:24











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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









15












$begingroup$

In general you can't. That is, if you have just two particles you cannot tell whether they are entangled or not.



Entanglement reveals itself by correlations. For example if you take many pairs of particles you may find that their properties are always correlated, e.g. their spins are always opposite, and this tells you that whatever mechanism is generating the pairs of particles is entangling them. But this shows up only with repeated measurements. A single measurement cannot tell you the particles are correlated since their spins could have the values you observe just by chance.






share|cite|improve this answer









$endgroup$












  • $begingroup$
    Thanks john, I assumed it involved measuring many pairs. I just wanted to confirm if correlation was the main thing we were looking for. Has anyone ever correlated two large objects which produced measurements of cos2?
    $endgroup$
    – Bill Alsept
    Mar 29 at 7:06











  • $begingroup$
    @BillAlsept That's very technically complicated. Measurement affects the object (as does any other interaction). The bigger the object, the harder it is to isolate from all those influences, and the harder it is to have any confidence in your measurement. There's no reason to expect entanglement "stops" at some scale, but there's many reasons to expect that the bigger the object, the harder it gets to prove entanglement. But we do know it works on a macroscopic scale, because quantum computers are macroscopic (without relying on entanglement of every individual atom involved).
    $endgroup$
    – Luaan
    Mar 29 at 9:21










  • $begingroup$
    @BillAlsept as far as I know this expt is the largest objects ever entangled
    $endgroup$
    – John Rennie
    Mar 29 at 12:07










  • $begingroup$
    @JohnRennie The article is very interesting but it says the two objects are coupled to a circuit and that the circuit keeps the two objects so called entangled. Isn’t that still just a local process? This is probably more of a question for chat But the only correlations I can think of are mirrored variables from a common source. Which is not really entanglement and why I say so called entanglement. I guess what I’m saying is I could draw up an experiment where many pairs of large objects are correlated with given variables that when tested would give the results of cos2. Thanks
    $endgroup$
    – Bill Alsept
    Mar 29 at 15:24















15












$begingroup$

In general you can't. That is, if you have just two particles you cannot tell whether they are entangled or not.



Entanglement reveals itself by correlations. For example if you take many pairs of particles you may find that their properties are always correlated, e.g. their spins are always opposite, and this tells you that whatever mechanism is generating the pairs of particles is entangling them. But this shows up only with repeated measurements. A single measurement cannot tell you the particles are correlated since their spins could have the values you observe just by chance.






share|cite|improve this answer









$endgroup$












  • $begingroup$
    Thanks john, I assumed it involved measuring many pairs. I just wanted to confirm if correlation was the main thing we were looking for. Has anyone ever correlated two large objects which produced measurements of cos2?
    $endgroup$
    – Bill Alsept
    Mar 29 at 7:06











  • $begingroup$
    @BillAlsept That's very technically complicated. Measurement affects the object (as does any other interaction). The bigger the object, the harder it is to isolate from all those influences, and the harder it is to have any confidence in your measurement. There's no reason to expect entanglement "stops" at some scale, but there's many reasons to expect that the bigger the object, the harder it gets to prove entanglement. But we do know it works on a macroscopic scale, because quantum computers are macroscopic (without relying on entanglement of every individual atom involved).
    $endgroup$
    – Luaan
    Mar 29 at 9:21










  • $begingroup$
    @BillAlsept as far as I know this expt is the largest objects ever entangled
    $endgroup$
    – John Rennie
    Mar 29 at 12:07










  • $begingroup$
    @JohnRennie The article is very interesting but it says the two objects are coupled to a circuit and that the circuit keeps the two objects so called entangled. Isn’t that still just a local process? This is probably more of a question for chat But the only correlations I can think of are mirrored variables from a common source. Which is not really entanglement and why I say so called entanglement. I guess what I’m saying is I could draw up an experiment where many pairs of large objects are correlated with given variables that when tested would give the results of cos2. Thanks
    $endgroup$
    – Bill Alsept
    Mar 29 at 15:24













15












15








15





$begingroup$

In general you can't. That is, if you have just two particles you cannot tell whether they are entangled or not.



Entanglement reveals itself by correlations. For example if you take many pairs of particles you may find that their properties are always correlated, e.g. their spins are always opposite, and this tells you that whatever mechanism is generating the pairs of particles is entangling them. But this shows up only with repeated measurements. A single measurement cannot tell you the particles are correlated since their spins could have the values you observe just by chance.






share|cite|improve this answer









$endgroup$



In general you can't. That is, if you have just two particles you cannot tell whether they are entangled or not.



Entanglement reveals itself by correlations. For example if you take many pairs of particles you may find that their properties are always correlated, e.g. their spins are always opposite, and this tells you that whatever mechanism is generating the pairs of particles is entangling them. But this shows up only with repeated measurements. A single measurement cannot tell you the particles are correlated since their spins could have the values you observe just by chance.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Mar 29 at 6:41









John RennieJohn Rennie

281k45563811




281k45563811











  • $begingroup$
    Thanks john, I assumed it involved measuring many pairs. I just wanted to confirm if correlation was the main thing we were looking for. Has anyone ever correlated two large objects which produced measurements of cos2?
    $endgroup$
    – Bill Alsept
    Mar 29 at 7:06











  • $begingroup$
    @BillAlsept That's very technically complicated. Measurement affects the object (as does any other interaction). The bigger the object, the harder it is to isolate from all those influences, and the harder it is to have any confidence in your measurement. There's no reason to expect entanglement "stops" at some scale, but there's many reasons to expect that the bigger the object, the harder it gets to prove entanglement. But we do know it works on a macroscopic scale, because quantum computers are macroscopic (without relying on entanglement of every individual atom involved).
    $endgroup$
    – Luaan
    Mar 29 at 9:21










  • $begingroup$
    @BillAlsept as far as I know this expt is the largest objects ever entangled
    $endgroup$
    – John Rennie
    Mar 29 at 12:07










  • $begingroup$
    @JohnRennie The article is very interesting but it says the two objects are coupled to a circuit and that the circuit keeps the two objects so called entangled. Isn’t that still just a local process? This is probably more of a question for chat But the only correlations I can think of are mirrored variables from a common source. Which is not really entanglement and why I say so called entanglement. I guess what I’m saying is I could draw up an experiment where many pairs of large objects are correlated with given variables that when tested would give the results of cos2. Thanks
    $endgroup$
    – Bill Alsept
    Mar 29 at 15:24
















  • $begingroup$
    Thanks john, I assumed it involved measuring many pairs. I just wanted to confirm if correlation was the main thing we were looking for. Has anyone ever correlated two large objects which produced measurements of cos2?
    $endgroup$
    – Bill Alsept
    Mar 29 at 7:06











  • $begingroup$
    @BillAlsept That's very technically complicated. Measurement affects the object (as does any other interaction). The bigger the object, the harder it is to isolate from all those influences, and the harder it is to have any confidence in your measurement. There's no reason to expect entanglement "stops" at some scale, but there's many reasons to expect that the bigger the object, the harder it gets to prove entanglement. But we do know it works on a macroscopic scale, because quantum computers are macroscopic (without relying on entanglement of every individual atom involved).
    $endgroup$
    – Luaan
    Mar 29 at 9:21










  • $begingroup$
    @BillAlsept as far as I know this expt is the largest objects ever entangled
    $endgroup$
    – John Rennie
    Mar 29 at 12:07










  • $begingroup$
    @JohnRennie The article is very interesting but it says the two objects are coupled to a circuit and that the circuit keeps the two objects so called entangled. Isn’t that still just a local process? This is probably more of a question for chat But the only correlations I can think of are mirrored variables from a common source. Which is not really entanglement and why I say so called entanglement. I guess what I’m saying is I could draw up an experiment where many pairs of large objects are correlated with given variables that when tested would give the results of cos2. Thanks
    $endgroup$
    – Bill Alsept
    Mar 29 at 15:24















$begingroup$
Thanks john, I assumed it involved measuring many pairs. I just wanted to confirm if correlation was the main thing we were looking for. Has anyone ever correlated two large objects which produced measurements of cos2?
$endgroup$
– Bill Alsept
Mar 29 at 7:06





$begingroup$
Thanks john, I assumed it involved measuring many pairs. I just wanted to confirm if correlation was the main thing we were looking for. Has anyone ever correlated two large objects which produced measurements of cos2?
$endgroup$
– Bill Alsept
Mar 29 at 7:06













$begingroup$
@BillAlsept That's very technically complicated. Measurement affects the object (as does any other interaction). The bigger the object, the harder it is to isolate from all those influences, and the harder it is to have any confidence in your measurement. There's no reason to expect entanglement "stops" at some scale, but there's many reasons to expect that the bigger the object, the harder it gets to prove entanglement. But we do know it works on a macroscopic scale, because quantum computers are macroscopic (without relying on entanglement of every individual atom involved).
$endgroup$
– Luaan
Mar 29 at 9:21




$begingroup$
@BillAlsept That's very technically complicated. Measurement affects the object (as does any other interaction). The bigger the object, the harder it is to isolate from all those influences, and the harder it is to have any confidence in your measurement. There's no reason to expect entanglement "stops" at some scale, but there's many reasons to expect that the bigger the object, the harder it gets to prove entanglement. But we do know it works on a macroscopic scale, because quantum computers are macroscopic (without relying on entanglement of every individual atom involved).
$endgroup$
– Luaan
Mar 29 at 9:21












$begingroup$
@BillAlsept as far as I know this expt is the largest objects ever entangled
$endgroup$
– John Rennie
Mar 29 at 12:07




$begingroup$
@BillAlsept as far as I know this expt is the largest objects ever entangled
$endgroup$
– John Rennie
Mar 29 at 12:07












$begingroup$
@JohnRennie The article is very interesting but it says the two objects are coupled to a circuit and that the circuit keeps the two objects so called entangled. Isn’t that still just a local process? This is probably more of a question for chat But the only correlations I can think of are mirrored variables from a common source. Which is not really entanglement and why I say so called entanglement. I guess what I’m saying is I could draw up an experiment where many pairs of large objects are correlated with given variables that when tested would give the results of cos2. Thanks
$endgroup$
– Bill Alsept
Mar 29 at 15:24




$begingroup$
@JohnRennie The article is very interesting but it says the two objects are coupled to a circuit and that the circuit keeps the two objects so called entangled. Isn’t that still just a local process? This is probably more of a question for chat But the only correlations I can think of are mirrored variables from a common source. Which is not really entanglement and why I say so called entanglement. I guess what I’m saying is I could draw up an experiment where many pairs of large objects are correlated with given variables that when tested would give the results of cos2. Thanks
$endgroup$
– Bill Alsept
Mar 29 at 15:24

















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