This is, as of yet, not recommended. Although you are logged in to our servers and your cards are saved, multi-device use is not recommended and not officially supported.
You are able to log into another device with your account and obtain all of your progress. You may even continue to progress from another device. However, it is not recommended that you switch devices frequently and multi-device use is not officially supported. For those that choose to do so, you may find that you are asked to complete a review session you already finished when you return to another device. Or, you may find that your progress of a review session on one device was not passed to the other.
You may run into this issue and others when using multiple devices. We are working to fully support multi-device use and will let you know when you may use all the devices you desire.
Here is a picture of a doggy, to hopefully make you a bit happier, until we have added this function: