Its a while I'm trying to understand [ http://arxiv.org/pdf/quant-ph/0108132v1.pdf ] but i have problem following its calculations.The part I have problem in now is the expansion in page 14,Eq. 50.Can anyone help me understand how that is done?(adsbygoogle = window.adsbygoogle || []).push({});

Thanks

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# Aid for understanding some calculations

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