Ultra 3R Duo

I got one years ago to try as a couples mat and it was way too small for us, but felt like a very nice one person mat. Great option if you really want to sprawl out in luxury and not have a car camping heavy mattress. 

Exped Ultra is comfortable and ultralight. Pretty affordable, too. Give it a try. 

I'm in the middle of research for an AT thru-hike with my boyfriend, so I've gotten pretty immersed in the world of two-person sleep setups. For a double quilt, the EE Accomplice is the move. There are a few other double quilts on the market, but this one seems to be the best reviewed. It's a big ticket item, but much cheaper than two quilts of the same quality and weight. For double pads, your options are the Big Agnes Rapide SL or the Exped 3r Ultra Duo. Both pads come in a 40 inch wide version, the width of two narrow pads, and a longer, wider version. It's up to you to figure out if you could sleep comfortably together on 40 inches of space, or if it's worth the substantial weight increase to carry a tent floor sized pad. The other option is to get two separate pads and coupler straps to join them together. This can be much lighter, and lets you customize the setup to each person's size. This is probably what we'll be doing, so my 6", 230 lb boyfriend can have a long wide pad, and I can have a regular mummy pad for minimal weight. If you're not trying to have two separate sleep systems with space in between, tent size won't be an issue. Look for a tent 52 inches wide, and you'll have no problem fitting the widest pads inside.

That is what I use . Works well

Exped duo.is the.goat

Exped 3R duo is excellent. Super comfortable with partner, love using it and also a very quiet pad.

seconding the Exped Ultra 3R Duo - the dual air chamber thing is exactly what OP needs since they specifically mentioned not wanting knock-on movement. the Medium is about 105cm wide too so it fits under that 120cm quilt constraint perfectly.

just a heads up - the Exped 3R is an inflatable pad, not CCF. if you specifically want closed cell foam, the RidgeRest Classic is the way to go from those two. if you're open to inflatables though, the Exped is way more comfortable for side sleeping since CCF pads are pretty thin and firm.

Great option for those that rock 2 person tents! Unfortunately the epxed duos won't fit in my 1p

The Exped pads are far and away the best. Comfortable, quiet, reasonable weights, and has two separate air chambers so one person moving doesn't disturb the other too much. They are not rectangular though, so if that's a hard requirement, they might not work. Pads I've tried * Exped Dura 5r Duo Medium (current go to car camping/winter double pad, heavy though) * Exped Ultra 3r Duo Medium (current go to backpacking double pad) * Exped Synmat Hyperlite Duo Medium (borrowed to try out before getting other Exped pads) * Big Agnes Rapide SL (returned, too thick and felt unstable with two people, especially with one air chamber) * Kylmit Double V insulated (sold, not very comfortable, not as warm as it should be, heavy) List of pads I haven't * Nemo has the Quesar, but it's quite heavy for the warmth and durability. * BA has the Divide, but it's really heavy * Paria has the Recharge DW which is heavy but has an rvalue of 4.7 and is cheap