you could ask your employer first to see if they will let you go early without notice.  If they do great, no one gets up set.  If they dont then ponder your options.

I already know that they wont be happy to see me leave. So I want to know what they law is and be well informed before I have this meeting!..Thanks peaky.

http://www.admin.ch/ch/e/rs/220/a337d.html

c. Failure to take up post and departure without just cause

1 Where the employee fails to take up his post or leaves it without notice without good cause, the employer is entitled to compensation equal to one-quarter of the employee’s monthly salary; in addition he is entitled to damages for any further losses.

2 Where the employer has suffered no losses or lower losses than the value of the compensation stipulated in the previous paragraph, the court may reduce the compensation at its discretion.

3 Where the claim for damages is not extinguished by set-off, it must be asserted by means of legal action or debt enforcement proceedings within 30 days of the failure to take up the post or departure from it, failing which it becomes time-barred.1

Your best bet is to negotiate it with both parties. Maybe the new job would be ok with you starting 1 week later and the old job would be ok with 3 weeks notice. Speak with them asap and try to find a solution, Normally a company doesn't want an amployee who is miserable around.

"Délais de congé

7 jours pendant le temps d’essai (pour la fin d’un jour)
1 mois pendant la première année de service (pour la fin d’un mois)
.... Les contrats de travail de durée déterminée prennent fin à l’expiration de la période convenue."

even with this short contract, did you have any clause stating that the notice period is 1 month? When is your contract supposed to end? I guess it'll be hard to say for sure which kind of penalties you might have without knowing which type of contract you signed.... Good luck!

It can only be a maximum of one month. The contracts before were also temporary and have now expired. Only confidentiality clauses can still apply, which could mean you can`t work for a competitor. Check your contract, as they only give you temp contracts for a year, the termination period can very well be less.Also I believe it`s highly doubtful they will take you to court over this if you would quit and walk out the same day. However, very probable they will not pay you everything they owe you, rather less or nothing at all.

Also note that Switzerland can be very small. Leaving a company in a bad way, can possibly bite you in the ass later.