Make sure you set your first portal to the left of the beam receiver located on the upper-left part of the ceiling.
The second portal should be placed on the nearest wall so you drop down onto the upper platform where the Displacement Cube is resting.
Place a new portal directly underneath the beam receiver and then look at where the laser beam on the left-hand wall is pointing to. Place your second portal here and this will allow the beam to reach the receiver and open up the first of the two locks.
The final piece of the puzzle requires you to pick up the Displacement Cube and jump across onto the platform in the centre of the room. Place it down so the laser is deflected right onto the last receiver, opening the final lock allowing you to leave this chamber.
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