Thank you for the question and picture. In order to achieve "closer cleavage" the capsule surrounding the breast implant will need to be opened in the cleavage area (medial capsulotimy). Sometimes, if there is a lateral breast implant displacement concern, the capsule in the lateral (axillary) area needs to be closed off (capsulorraphy). Selection of appropriate breast implant size/profile will be important also.
Communicate your goals/concerns/questions directly with your plastic surgeon preferably in front of a full-length mirror with the help of goal photographs. Make sure that you are both on the same page prior to proceeding. Best wishes for an outcome that you will be pleased with long-term.
If you implants are under the muscle, then moving them closer together needs to be considered carefully because it is the attachment of the muscle along the side of the breast bone that prevents the implants from being closer. If the muscle is detached in order to narrow the cleavage, you can get symmastia and severe animation issues. It can be done up to a point but it depends on your anatomy. Also note that the implants are centered behind your nipples. If you move them closer together then the nipples will appear to be on the lateral part of the breasts. You may need a wider implant to balance these things out.
When breast implants are first placed, a pocket is created. The pocket for the implants becomes lined with a thin layer of scar-like tissue we call the capsule. This capsule limits the movement of the implants. The capsule will start to the outside of the middle of the chest. If it begins several centimeters to the side of the chest then this limits the cleavage a patient can obtain. To remedy this situation, we can sometimes go back to the capsule and remove or release the capsule. This lets the implants lie closer to the middle of the chest and enhance the ability to obtain cleavage.