# Re: Can someone explain why this doesn't work?

`On Fri, Jul 26, 2013 at 3:57 PM, John Clark <johnkcl...@gmail.com> wrote:`
```
> On Fri, Jul 26, 2013Jason Resch <jasonre...@gmail.com> wrote:
>
> > If a photon passes a filter orientated at 0 degrees, then it encounters
>> a filter at 90 degrees it will be blocked.
>>
>
> How do you know the photon is oriented at 0 degrees?
>

Because it passed a filter orientated at 0 degrees.

> If the photon has never been measured, if neither it nor its entangled
> twin has ever passed through a filter of any sort before and now for the
> first time it encounters a filter set at 90 degrees, or set at ANY other
> angle, the probability it will be blocked by the filter is 50 50.
>
>
>>   > But, if you insert a filter in the middle orientated at 45 degrees
>> then there is a 50% chance it will continue through that filter after
>> passing the 0 degree filter, and also a 50% chance that that photon will
>> also pass the filter at 90 degrees.  Therefore there is a 25% chance a
>> photon that passes the filter at 0 degrees passes the next 2 filters.
>>
>
> Yes, and one chance in 8 that a previously unmeasured undifferentiated
> photon will make it through all 3 filters.
>

Yes, like I said.

>
> >> If my differentiated photon with a known polarization encounters a
>>> filter that its brother photon has not then the delicate quantum
>>> entanglement between the two is destroyed and there are just 2 unrelated
>>> photons a billion light years away
>>
>>
>> >I don't think that is correct.
>>
>
> It is correct, measurement can be very detrimental to quantum
> entanglement, that's why making a quantum computer is so difficult.
>
> > If a photon passes a 0 degree filter,
>>
>
> Then it has always been orientated at 0 degrees and so has its entangled
> twin, if you then put a filter set at 45 degrees in the photon's path there
> is a 50 50 chance it will get through, but get through or not the
> entanglement will have been destroyed unless somebody a billion light years
> away also put a filter set at 45 degrees in the distant photon's path.
>
>  > the twin photon a billion light years away will always be stopped by a
>> 90 degree filter.
>>
>
> Yes,
>

So why is it the entanglement is destroyed by the presence of the 45 degree
filter, but not the 0 degree filter?

Jason

> but there is no way to use that fact to send a message, because I have no
> way of forcing a unmeasured photon make it through my filter or be blocked
> by it, the chances are always 50 50; so I have no way to send a dot instead
> of a dash or a dash instead of a dot, so the only message I can send is
> random gibberish.
>
>  John K Clark
>
>
>
>
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