The principle states: δxδp≥h/4π I understand what it means and ive seen in proven both theoretically and expiamentally, so im not questioning the inequality here. My question is: If there was a very narrow tube that had a vacuum inside it and a laser attached at one end that shoots single photons. The tube is black on the outside so no light can get inside, there are 'perfect mirrors' all around the inside so no light could be lost, why cant we know a photons position and momentum at the same time now? I mean assuming we know its energy when it leaves the laser, its velocity, and the dimentions of the of the vacuum tube, why cant we always know the photons displacement and momentum at any instantanious moment in time? Thank you!