Questioner: There is Jagrat (waking), Swapna (Dream) and Sushupti (Deep sleep), the three avasthas (states) that have distinct qualities. Is there something else called Jagrat Sushupti (waking sleep)? Please can you explain?

Tom: Regarding Jagrat Sushupti, see the Annapurna Upanishad 2.12 and 2.13:

2.12. The quiescent state of the attenuated mind, free from all objective reference [Tom: ie. nirvikalpa samadhi], is said to be the deep sleep in wakefulness (Jagrat-Sushupti).

2.13. This state of slumber, O Nidagha, fully developed through practice, is styled the Fourth (Turiya) by the best knowers of Truth.

Note the term Turiya, or The Fourth, means the state of being the Self, also known as Moksha or Jnana. Here we can see that Jagrat Sushupti, Moksha, Turiya and (by implication) Nirvikalpa Samadhi are all being equated.

Sri Ramana Maharshi explains this teaching of Jagrat Sushupti in more detail in Talks with Sri Ramana Maharshi, talk 609:

‘The incentive to realise can arise only in the waking state and efforts can also be made only when one is awake. We learn that the thoughts in the waking state form the obstacle to gaining the stillness of sleep.

“Be still and know that I AM God”.

‘So stillness is the aim of the seeker. Even a single effort to still at least a single thought even for a trice goes a long way to reach the state of quiescence. Effort is required and it is possible in the waking state only. There is the effort here: there is awareness also; the thoughts are stilled; so there is the peace of sleep gained. That is the state of the Jnani. It is neither sleep nor waking but intermediate between the two. There is the awareness of the waking state and the stillness of sleep. It is called jagrat-sushupti.

‘Call it wakeful sleep or sleeping wakefulness or sleepless waking or wakeless sleep. It is not the same as sleep or waking separately. It is atijagrat (beyond wakefulness) or atisushupti (beyond sleep).

‘It is the state of perfect awareness and of perfect stillness combined. It lies between sleep and waking; it is also the interval between two successive thoughts. It is the source from which thoughts spring; we see that when we wake up from sleep. In other words thoughts have their origin in the stillness of sleep. The thoughts make all the difference between the stillness of sleep and the turmoil of waking.

‘Go to the root of the thoughts and you reach the stillness of sleep. But you reach it in the full vigour of search, that is, with perfect awareness. That is again jagrat-sushupti spoken of before. It is not dullness; but it is Bliss. It is not transitory but it is eternal.’

~Sri Ramana Maharshi, Talks with Sri Ramana Maharshi, talk 609

This teaching of Jagrat Sushupti is more fully explained in this post here.