According to Israel’s Ministry of Health directives, a person in quarantine is to remain in a separate room and have no physical contact at all with other members of the family.
Halachically, you are required to adhere carefully to instructions like these, intended to prevent danger to others’ lives. Accordingly, having relations with your husband in quarantine would be prohibited.
We do still recommend immersing on time, although if your scheduled night is particularly inconvenient you can put it off.
Note: Even if a couple are in quarantine together (e.g., because they were exposed at the same time or returned together from a trip abroad, or because they have young children in quarantine), intimate relations are not recommended during quarantine. This is because one person may become ill and the other not, and relations are a form of close contact that can easily spread Covid-19. Of course, a woman in quarantine may not visit the mikveh, so this would be relevant only if she were already tehorah.